ULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


NO.  528 


i 


j 


Science  Series,  Vol.  4,  No.  s,  pp.  izs-m 


THE  CLASSIFICATION  OF  CARBON  COMPOUNDS 


BY 


EDWARD  KREMERS,  Ph.D. 

Professor  of  Pharmaceutical  Chemistry 
The  University  of  Wisconsin 


CONTRIBUTIONS  FROM  THE  COURSE  IN  PHARMACY 


MADISON,  WISCONSIN 
1912 


Reprinted  1924 
Price,  $1.00 


table  of  contents 


54-7 

Kztc. 

(LO  p*  *2-* 


& Preface 5 

O Definition  of  organic  chemistry 7 

O History  of  chemical  organic  classification 10 

A rational  system  of  the  classification  of  carbon  compounds  based  on 

their  structure 17 

Classification  of  the  hydrocarbons 17 

Kekule’s  structural  considerations  based  on  the  quadrivalence 

of  the  carbon  atom 17 

The  limit  formula  of  saturation  and  formulae  of  lesser  satu- 
ration; degrees  of  saturation 18 

The  structural  equivalents  of  pairs  of  hydrogen  atoms 31 

The  double  bond  T 31 

The  cycle  A 31 

The  treble  bond  p 31 

Table  of  types  of  hydrocarbons 31 

Table  of  structural  equivalents 31 

Classification  of  the  substitution  products  of  the  hydrocarbons ....  32 

The  three  simple  hydrocarbon  groups  the  basis  of  simple  types  32 

Extent  of  substitution 32 

Substitution  in  connection  with  the  same  carbon  atom 33 

Halogen  substitution  products 33 

Hydroxy  substitution  products  and  their  dehydration 

products 34 

Amido  substitution  products  and  their  deammonation 

products 36 

Other  substitution  products 37 

Genetic  relationship  of  types 38 

Mono 40 

Di 41 

Tri 42 

Substitution  in  connection  with  different  carbon  atoms 45 

Multiplication  of  types 45 

Heterocyclic  compounds 48 

Containing  C,  H and  O 

Containing  C,  H and  N 


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in  2017  with  funding  from 

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https://archive.org/details/classificationofOOkrem 


PREFATORY  REMARKS 


“Arbeit  allein  kann  die  Licht 
gebenden  Ideen  nicht  herbeizwin- 
gen.  Etwas  vom  Schauen  des 
Dichters  muss  auch  der  Forscher 
in  sich  tragen.” 

Helmholtz. 


“La  science  ne  consiste  pas  en 
faits,  mais  dans  les  consequences 
que  l’on  en  tire.” 

At  the  annual  meeting  of  the  Wisconsin  Academy  of  Sciences, 
Arts,  and  Letters  in  December,  1894,  the  writer  read  a paper 
“On  the  Classification  of  Carbon  Compounds,”  which  was  pub- 
lished in  the  Transactions1  of  that  body.  The  introductory 
paragraph  may  here  be  quoted: 

“In  the  winter  semester  of  1888-9,  Professor  August  Kekuld, 
in  his  course  on  the  chemistry  of  the  carbon  compounds  at  the 
University  of  Bonn,  Germany,  introduced  the  subject  of  fatty  al- 
cohols, aldehydes,  ketones,  acids,  hydroxy  acids,  etc.,  by  a lec- 
ture in  which  he  gave  a general  survey  of  the  theoretically  pos- 
sible hydroxy  derivatives  of  the  paraffin  hydrocarbons.  I sup- 
pose it  was  Prof.  Kekul4’s  usual  method  of  treating  the  sub- 
ject, but  I am  not  warranted  in  making  so  broad  a statement. 
However,  this  theoretical  introduction  is  fully  in  harmony  with 
the  methods  of  teaching  of  this  genial  lecturer,  known  and  cele- 
brated not  so  much  for  the  compounds  he  has  discovered,  but  for 


1 Vol.  10,  p.  310.  A second  paper  was  read  ten  years  later,  but  not  published.  At 
the  Baltimore  meeting  of  the  American  Chemical  Society  in  1909,  a twenty-minute  paper 
on  the  same  subject  was  read  by  request  at  a general  meeting  of  the  Association. 

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his  theories,  that  have  prophesied  the  possibility  of  hosts  of 
compounds,  which  have  been  prepared  by  others  in  the  attempt 
to  establish  as  well  as  in  the  attempt  to  overthrow  Prof.  Kekule’s 
theories.” 

If  honest  confession  be  good  for  the  soul,  the  above  paragraph 
ought  to  suffice  to  show  that  the  writer  makes  no  great  claim 
for  originality  and  at  the  same  time  it  reveals  the  source  of  his 
inspiration.  All  that  the  writer  claims  is  that  he  has  endeavored 
to  systematize  by  means  of  logical  questions  and  answers. 

The  problem  of  rational  classification  of  the  carbon  compounds 
is  one  of  those  that  can  not  be  worked  out  in  the  research  lab- 
oratory, but  has  to  be  solved  primarily  in  the  class  room.  Now, 
that  after  more  than  twenty  years  of  experience  in  this  direc- 
tion the  system  has  revealed  its  advantages  not  only  in  the  class 
room  of  the  writer  but  in  the  class  rooms  of  his  former  students 
as  well,  the  time  seems  to  have  arrived  when  the  more  completely 
worked  out  system  should  be  given  wider  publicity. 

However,  while  the  system  had  to  be  tried  out  in  the  class- 
room, the  conference,  and  the  seminar,  it  has  found  useful  appli- 
cation in  laboratory  research.  As  applied  to  the  sesquiterpenes,2 
as  representatives  of  the  hydrocarbons,  it  has  evidently  proven 
acceptable  to  others.3 

In  the  systematic  study  of  the  glucosides,  pigments,  and  alka- 
loids it  has  brought  out  relationships  formerly  not  apparent. 
An  attempt  is  also  being  made  to  make  the  organic  laboratory 
manual  something  more  than  a collection  of  working  formulas, 
and  suggestions  for  reading.  As  to  details,  the  writer  hopes  to 
find  the  time  to  bring  the  entire  materia  phytochemica  into  con- 
formity with  this  system  and  thus  to  show  the  numerous  practical 
as  well  as  theoretical  advantages  which  it  possesses. 

It  may  be  suggested  that  the  time  is  not  opportune  for  a re- 
vision of  the  classification  of  carbon  compounds  on  the  basis  of 
structural  atomic  chemistry,  since  the  atoms  are  about  to  be 
replaced,  in  chemical  thought,  by  electrons.  Such  a sugges- 
tion, however,  is  not  likely  to  be  well  received  so  long  as  even 


* O.  Schreiner,  The  sesquiterpenes,  p.  17. 

* Comp.  " Neuere  Eintheilung  der  Sesquiterpene”  in  Arnold  Lewinsohn,  Beitraege  tur 
Kennlniss  der  Sesquiterpene,  lnnaugural-Dissertation,  Leipzig,  1908,  p.  14. 

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KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  7 


physicists  warn  chemists  “not  to  be  too  ready  to  throw  away 
conceptions  (such  e.  g.,  as  that  of  an  atom)  . . . that  have  proved 
very  valuable  as  aids  to  the  advancement  of  science  in  the  past.”4 

However  valuable  the  theory  of  electrons  may  prove,  it  may  be 
a generation  or  more  before  it  can  affect  our  ideas  of  the  classi- 
fication of  carbon  compounds,  should  it  ever  exert  such  an  in- 
fluence. While  we  should  always  welcome  new  tools  and  learn 
to  use  them  if  possible,  it  would  be  foolish  indeed  to  discard  an 
old  tool,  simply  because  a new  one,  which  we  have  not  learned 
to  use,  is  in  sight.6 

All  that  the  writer  asks  for  the  suggestions  toward  the  rational 
classification  of  the  carbon  compounds  is  that  they  be  given  a 
fair  trial.  He  fully  realizes  that  in  such  matters  changes  are 
not  likely  to  come  about  with  revolutionary  suddenness,  but 
that  old  habits  of  thought  must  be  gradually  overcome  by  the 
slow  process  of  evolution. 


DEFINITION  OF  ORGANIC  CHEMISTRY 

For  the  purpose  of  this  study  organic  chemistry  is  defined 
as  the  chemistry  of  the  hydrocarbons  and  their  substitution 
products.  Not  that  this  definition  covers  ground  other  than  that 
covered  by  the  definition  mostly  in  vogue  at  the  present  time, 
viz.,  that  organic  chemistry  is  the  chemistry  of  the  carbon  com- 
pounds, but  that  the  definition  suggested  has  this  advantage  in 
the  study  of  classification  and  nomenclature  that  it  emphasizes 
two  important  lines  of  thought  and  development.  First,  it 
emphasizes  the  fact  that  the  hydrocarbons,  the  simplest  of  car- 
bon compounds,  are  to  be  regarded  as  basal  compounds  and  that 
all  other  carbon  compounds  are  to  be  derived  from  these  hydro- 
carbons by  the  process  of  substitution. 


* President  Richard  G.  MacLaurin  of  Mass.  Inst,  of  Tech,  at  the  banquet  of  the  A.  C.  S. 
Science,  32,  p.  10. 

* It  would  be  more  than  foolish  for  the  accomplished  piano  player  to  abandon  his  instru- 
ment at  the  age  of  twenty-five  or  more  because  he  has  become  convinced  that  the  violin 
is  the  more  perfect  musical  instrument.  While  a successful  pianist,  he  might,  and,  in 
all  probability,  would,  achieve  only  mediocrity  with  the  violin.  The  same  reasoning  ap- 
plies to  the  present  day  chemist  and  his  possible  change  from  the  atomic  to  the  electron  theory. 

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Kolbe  at  one  time  suggested  that  all  carbon  compounds  be 
derived  from  carbon  dioxide  from  which  the  plant  synthesizes 
its  complex  carbon  compounds.  But  though  we  could  follow 
the  synthetic  processes  of  the  plant  much  better  than  we  can 
even  today,  no  one  would  any  longer  think  of  following  such  a 
suggestion  for  purposes  of  classification  or  nomenclature.  Our 
knowledge  of  the  hydrocarbons,  however,  is  such  that  today  they 
universally  serve  as  the  basal  compounds,  not  only  for  purposes 
of  classification  and  nomenclature  but  for  didactic  purposes  as 
well.  What  we  need  at  present  is  a more  rational  classification 
of  these  basal  hydrides  of  carbon  than  is  commonly  found  in 
organic  chemical  literature. 

The  second  basal  thought  suggested  by  the  definition  is,  as  al- 
ready pointed  out,  that  all  other  carbon  compounds  be  derived 
from  the  hydrocarbons  by  the  process  of  substitution.  In  re- 
search work,  in  preparation  work,  and  also  in  analytical  proc- 
esses we  make  extensive  use  of  the  additive  capacity  of  com- 
pounds. 

We  need  in  no  wise  underestimate  the  importance  of  the  ad- 
dition product  because  addition  is  not  universally  applicable, 
yet  this  is  more  than  sufficient  reason  for  not  adopting  it  as  a basal 
process  in  a system  of  classification  and  nomenclature.  Neither 
can  we  for  this  purpose  adopt  advantageously  any  other  than  a 
Unitarian  point  of  view.  What  we  need  in  organic  classifica- 
tion and  nomenclature  is  to  get  rid,  for  the  purpose  under  con- 
sideration, of  points  of  view  based  on  totally  different  concep- 
tions, such  as  the  old  dualistic  view  of  acids,  bases,  and  salts, 
that  of  the  theory  of  types,  etc. 

The  term  organic  chemistry  is  said  to  have  been  introduced 
by  Bergmann  who  pointed  out  that  there  was  no  fundamental 
difference  between  the  chemical  compounds  from  the  vegetable 
and  animal  kingdoms.  Previous  to  his  time  the  materia  chem- 
ica,  and  with  it  chemical  science,  was  divided  according  to  the 
source  of  the  material  from  the  mineral,  vegetable,  and  animal 
kingdoms.  In  this  chemists  had  followed  the  suggestion  by 
Emanuel,  who  in  1682  classified  all  terrestrial  objects  according 
to  their  relation  to  one  of  these  natural  kingdoms.  However, 
organic  chemistry  was  long  thereafter  still  subclassified  into 
vegetable  chemistry  and  animal  chemistry. 

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KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  9 


The  student  of  organic  chemistry  is  usually  told  that  by  his 
so-called  synthesis  of  urea,  Woehler  in  1828,  dealt  the  death- 
blow to  the  notion  that  organic  chemistry  is  the  chemistry  of 
the  functions  of  organs  and  their  products,  in  other  words  of 
that  mysterious  something  called  life.  Yet  Woehler’s  so-called 
synthesis  was  no  synthesis  at  all,  but  an  inversion,  an  intra- 
molecular re-arrangement  of  the  atoms  of  one  molecule  to  an- 
other of  like  size.  Neither  did  Woehler’s  noteworthy  and  far- 
reaching  observations  immediately  influence  chemical  thought, 
at  least  so  far  as  definition  and  classification  reflected  the  ad- 
vance of  chemical  thought.  Even  Gmelin  stated  that  “the 
bodies  of  the  organic  kingdom  are  distinguished  in  their  most 
complete  state,  from  those  of  the  inorganic  kingdom  . . . 
by  being  composed,  for  the  principal  and  most  important  part 
at  least,  of  chemical  compounds  quite  peculiar  to  them,  called 
organic  compounds  . . . ’n 

Today  we  have  gotten  away  completely  from  any  significance 
of  life  so  far  as  the  concept  organic  chemistry  is  concerned. 
That  branch  of  chemistry  which  deals  with  the  so-called  life 
processes  of  plants  and  animals  is  termed  biochemistry  and  rep- 
resents a line  of  chemical  activity  as  does  phytochemistry  and 
zoochemistry.  Organic  chemistry  is  universally  interpreted  at 
present  as  implying  the  chemistry  of  the  carbon  compounds  irre- 
spective of  source  or  mode  of  formation.  The  term  carbon 
has  reference  to  elemental  composition  and  could  not  have  been 
used  before  the  recognition  of  the  modern  elements  since  the 
close  of  the  18th  century.  Indeed,  its  use  in  the  sense  as  quoted 
above  is  of  much  more  recent  date.  The  first  to  have  suggested 
the  definition  of  organic  chemistry  as  the  chemistry  of  carbon 
appears  to  have  been  Gerhardt  as  early  as  1844  or  possibly 
earlier.1 2  Kekule  then  suggested  that  we  “define  organic  chem- 
istry as  the  chemistry  of  the  carbon  compounds.”3  This  def- 
inition-subtitle was  accepted  by  Richter,  one  of  the  disciples  of 
Kekul4  and  author  of  the  well-known  text  which  has  been  re- 


1 For  a more  detailed  statement  see  Appendix:  Definitions  of  organic  chemistry. 

* See  Appendix:  Definitions  of  organic  chemistry. 

3 See  Appendix:  Definitions  of  organic  chemistry. 


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peatedly  revised  by  Anschuetz  and  translated  into  English  by 
Smith.4 

As  a mere  definition  this  will  do  as  well  as  any  other  especially 
if  interpreted  in  the  light  of  Kekule’s  commentary,5  but  if  our 
definition  is  to  point  logically  to  the  method  of  classification, 
as  the  classification  should  reflect  the  most  satisfactory  chemical 
theories,  then  it  is  no  longer  satisfactory  for  purposes  such  as 
are  here  to  receive  consideration.  Hence  for  our  present  needs 
we  prefer  to  define  organic  chemistry  as  the  chemistry  of  the 
hydrocarbons  and  their  substitution  products.  A careful  perusal 
of  the  principles  of  classification  will,  no  doubt,  be  found  to 
justify  the  adoption  of  this  definition  which  is  equally  valuable 
from  a didactic  point  of  view. 


HISTORY  OF  ORGANIC  CHEMICAL  CLASSIFICATION 


In  order  to  give  proper  expression  to  chemical  ideas,  a chemi- 
cal language  has  been  developed  which  reflects  chemical  thought. 
Science,  we  are  told,  consists  not  of  fats,  but  in  the  conclusions 
which  we  draw  from  them.  Some  of  the  most  important  con- 
clusions drawn  from  chemical  facts  have  been  derived  by  sys- 
tematization of  the  materia  chemica.  As  a result,  general  theory 
and  chemical  classification  have  developed  side  by  side,  so  that 
the  study  of  the  history  of  classification  reflects  in  no  small  part 
the  advance  made  in  general  chemical  theory. 

A review  of  the  principal  systems  of  classification  of  the  past 
hundred  years  and  more,  clearly  reveals  the  fact  that  the  ra- 
tional systems  of  classification  were  based  largely  on  structural 
theories,  structural  of  necessity,  in  the  varying  sense  in  which 
this  concept  was  interpreted  from  time  to  time.  The  temporary 
breakdown  of  structural  conceptions  during  the  middle  of  the 
nineteenth  century,  when  atoms  had  to  give  way  to  equivalents, 
gave  rise  to  a condition  bordering  on  anarchy  not  only  in  classi- 


4 Victor  von  Richter’s  Organic  Chemistry  or  Chemistry  of  the  Carbon  Compounds.  Edited 
by  R.  Anschuetz.  Authorized  translation  by  E.  F.  Smith,  1899. 

•See  Appendix:  Definitions  of  organic  chemistry. 

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KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  11 


fication  but  in  general  chemical  thought.  The  arrangement 
of  carbon  compounds  according  to  the  number  of  carbon  atoms* 
is  no  more  a rational  classification  than  the  arrangement  of  plants 
according  to  the  number  of  the  stamens  of  their  flowers.  Such 
an  artificial  arrangement,  while  of  value  in  the  tracing  of  ana- 
lytical results  based  on  elementary  analysis* 1  does  not  afford  for 
most  purposes  even  the  convenience  of  the  alphabetical  arrange- 
ment of  the  chemical  dictionary  or  encyclopedia. 

Previous  to  the  chemistry  of  oxygen,  as  elucidated  by  Lavois- 
ier, there  was  no  organic  chemistry  in  name,  and  but  few  car- 
bon compounds  had  been  isolated  or  prepared  artificially.2  Yet 
in  order  to  understand  later  developments,  it  seems  advisable 
to  go  back  as  far  as  Lemery  and  one  of  the  first  chemical  texts 
free  from  alchemistic  jargon,  his  Coitrs  de  ckimie. 

Following  the  classification  of  all  natural  objects  (and  beings) 
into  three  natural  kingdoms,  the  regna  naturae,  suggested  by 
Emanuel  in  1682,  Lemery  arranged  the  subject  matter  of  his 
Course  in  Chemistry  under  these  headings: 

(1)  Upon  minerals 

(2)  Upon  vegetables,  and 

(3)  Upon  animals. 

As  early  as  1780,  Bergmann  began  to  distinguish  organic  from 
inorganic  bodies,  having  shown  that  the  same  organic  substances 
can  be  obtained  from  both  the  vegetable  and  animal  kingdoms. 
Nevertheless,  the  classification  of  the  organic  materia  chemica 
according  to  the  two  kingdoms  of  organized  nature,  namely  the 
vegetable  and  animal  was  upheld  for  a long  time. 

Thus  Lavoisier,  whose  principal  point  of  view  was  that  of 
oxygen  first,  last,  and  all  the  time,  separates  the  carbon-con- 
taining acids  obtained  from  the  vegetable  kingdom  from  those 
obtained  from  the  animal  kingdom.  This  separation  is  found 
even  in  the  third,  rewritten  and  revised  edition  of  Lavoisier’s 
“Traite  eUmentaire  de  chimie ” of  1801. 

Fourcroy,  one  of  Lavoisier’s  associates  on  the  Commission  of 
Chemical  Nomenclature  according  to  the  antiphlogistic  system, 

* See  Appendix:  Arrangement  according  to  number  of  carbon  atoms. 

1 Compare  Richter’s  Lexikon  der  Kohlenstoff-Verbindungen,  and  the  Formel-register 
of  the  Berichte  der  deutschen  chemischen  Gesellschaft  based  on  the  same  principle. 

2 See  Appendix:  Classification  as  revealed  by  tables  of  contents. 

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likewise  distinguished  between  “les  composes  vegetaux ”3 4  and 
the  “ substances  animates.”* 

Berzelius,  the  great  generalizer  of  his  time,  in  his  epoch-making 
“Lehrbuch  der  Chemie”  does  likewise,  even  in  the  third  edition 
published  in  1837.  His  organic  chemistry  is  subdivided  into 
“ Plant  Chemistry ”5  and  “ Animal  Chemistry .”6 

With  such  classical  examples  as  guides,  it  is  not  surprising 
that  other  authors  followed  even  up  to  the  middle  of  the  nine- 
teenth century.  Thus  this  system  of  classification  long  out- 
lived its  theoretical  usefulness. 

Whatever  may  be  said  for  or  against  the  designation  of  La- 
voisier as  the  founder  of  chemical  science,  this  much  is  undeniably 
true  that  his  antiphlogistic  theories  placed  chemical  classification 
and  nomenclature  on  a new  basis.  As  already  pointed  out, 
the  chemistry  of  Lavoisier  was  the  chemistry  of  oxygen  just  as 
the  predominant  chemistry  of  Kekul4  and  of  the  generation  of 
chemists  that  followed  him  was  a chemistry  of  carbon,  even  more 
so.  The  oxides  of  the  metals  were  designated  bases,  the  oxides 
of  the  nonmetals,  acids,  both  binary  compounds,  and  the  union 
of  the  two  resulted  in  the  ternary  compounds  or  salts  which  nat- 
urally also  contained  oxygen.  Thus  there  was  laid  the  founda- 
tion for  the  electrochemical  theories  of  Davy  and  the  dualistic 
structural  theories  of  Berzelius.  The  discovery  of  the  halogens 
and  their  derivatives  naturally  modified  these  views  but  they  did 
not  revolutionize  them.  Indeed  we  today  are  still  under  the 
ban  of  the  antiquated  theory  of  acid,  base  and  salt. 

Compared  with  the  inorganic  field,  organic  chemistry  as  de- 
fined by  Bergmann  played  but  a minor  role  though  it  was  being 
enriched  by  Scheele  and  other  phytochemists.  Yet  organic 
chemistry  had  its  organic  acids  comparable  to  the  inorganic  acids, 
it  also  had  its  inorganic  salts  of  these  organic  acids.  The  organic 
base,  however,  was  wanting  until  Sertuerner  discovered  it  in 
morphine,  this  “new  salifyable  plant  base”  as  he  called  it.  This 
morphine  attracted  universal  attention,  not  because  it  had  been 


* Systeme  des  connaissances  chimique  (Bumaire,  An.  IX),  tomes  7 et  8. 

4 Ibidem,  tomes  9 et  10. 

‘ Vols.  6,  7 and  8 of  the  3rd  German  edition  of  1837. 

6 Vol.  No.  9 of  the  same  edition. 


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KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  13 


isolated  from  opium,  for  such  isolation  had  been  effected  inde- 
pendently by  both  Derosne  and  Sertuerner  more  than  a dozen 
years  before,  but  because  Sertuerner  had  recognized  its  basic, 
i.  e .,  its  salt-forming  properties.  Thus  the  parallel  between 
organic  chemistry  and  inorganic  chemistry  was  thought  to  have 
been  established. 

This  satisfaction,  however,  was  of  but  short  duration  for  chem- 
ists soon  realized  the  importance  of  the  fact,  already  hinted  at 
by  Sertuerner,  that  morphine  and  the  alkaloids  discovered  in 
rapid  succession,  were  related  to  the  inorganic  ammonia,  rather 
than  to  the  oxygen  bases  of  the  metals. 

The  conception  of  this  parallel,  however,  seemed  too  good  to 
be  abandoned,  so  it  was  revived  by  Liebig  who  pointed  out  that 
the  organic  alcohol  was  the  true  analogue  of  the  inorganic  base 
as  the  organic  acid  was  that  of  the  inorganic  oxygen  acid.  In 
like  manner  the  product  of  the  union  of  organic  acid  and  alcohol, 
the  etheral  salt  or  ester,  was  regarded  as  the  analogue  of  the 
inorganic  salt.  Thus  there  was  re-established  the  true  analogy 
between  organic  chemistry  and  inorganic  chemistry,  and  organic 
chemistry  was  defined  the  chemistry  of  the  compound  radicle 
by  Liebig,  the  alkyl  or  positive  radicle  corresponding  to  the  metal, 
the  acyl  or  negative  radical  to  the  non-metal. 

Whereas  the  difficulties  of  the  inorganic  system  were  patched 
up  by  coining  new  names,  such  as  halogen  acids  and  halides, 
thioacids  and  thionates,  the  difficulties  of  the  organic  field  would 
not  be  downed  by  coining  such  words  as  neutral  principles,  i.  e., 
substances  that  were  neutral  in  themselves  and  not  by  virtue  of 
the  neutralizing  power  of  acid  upon  alkali  or  vice  versa . Yet 
in  organic  chemistry  as  in  inorganic  chemistry  we  are  still  la- 
boring under  the  ban  of  opposites,  of  acids  and  alcohols,  which 
instead  of  being  regarded  primarily  as  opposites  should  rather 
be  looked  upon  as  related  compounds. 

The  difficulties  arising  from  the  ever  growing  number  of  car- 
bon compounds  were  not  solved  by  creating  new  classes  of  com- 
pounds or  by  relegating  them  to  an  ever  convenient  lumber 
chamber.  The  conception  of  the  rigid  radicle,  this  element,  so- 
called,  of  organic  chemistry,  had  to  be  abandoned  in  the  light  of 
the  theory  of  substitution.  The  concept  of  homology,  though 

[141] 


14  bulletin  of  the  university  OF  WISCONSIN 

it  aided  materially  in  throwing  light  on  difficult  problems,  did 
not  remove  the  more  fundamental  difficulties  of  the  situation. 
Neither  did  the  theory  of  types,  though  it,  more  than  any  one 
other  conception,  aided  in  bringing  order  into  chaos,  and  though 
it  paved  the  way  for  the  structural  theories  of  Kekule. 

All  of  these  theories  and  views  are  reflected  in  chemical  no- 
menclature and  classification.  These  reflections  are  found  not 
only  in  the  chemical  history  of  the  past  century,  but  in  our  pres- 
ent day  mode  of  chemical  thought  and  language.  While  useful 
at  times,  they  often  linger  as  an  obstructing  “spuk”  just  as 
the  life  “spuk”  of  organic  chemistry  has  made  its  presence  felt 
again  and  again  and  has  not  been  downed  completely  even  today. 
The  manner  in  which  these  ideas  are  reflected  in  chemical  classi- 
fication can  best  be  seen  from  the  tables  of  contents  of  contem- 
porary treatises  on  chemistry. 

The  structural  conceptions  of  Kekule  are  too  well  known  to  be 
reviewed  here.  How  he  arrived  at  them  he  himself  has  told  us  in 
his  after  dinner  speech  of  1890  at  the  celebration  of  the  twenty- 
fifth  anniversary  of  the  benzene  theory.7  How  he  worked  out 
his  structural  or  graphic  formulas  is  best  shown  in  some  of  the 
considerations  of  the  next  chapter. 

Frankland  having  recognized  the  tetravalence  of  the  carbon 
atom,  Kekule  added  the  type  methane  to  the  older  types  am- 
monia, water,  hydrohalogen  and  hydrogen.  The  structural  con- 
ception of  the  hydrocarbons  of  the  methane  series  and  of  their 
halogen  and  hydroxy  substitution  products  resulted.  These, 
together  with  the  olefine  and  acetylene  hydrocarbons  and  their 
respective  derivatives  were  grouped  together  as  fatty  compounds. 
His  conception  of  the  structure  of  benzene  added  still  a new 
type  and  its  homologues  and  their  derivatives  were  grouped 
together  as  aromatic  compounds. 

Great  as  was  the  advance  made  by  Kekule  in  his  classifica- 
tion there  is  today  no  more  justification  in  adhering  to  it  than 
to  the  notion  of  acids  and  bases.  Both  conceptions  emphasize 
opposites  whereas  the  relation  of  gradual  evolution  is  the  im- 
portant point  to  be  emphasized.  Opposition  becomes  apparent 


7 Berichte,  23,  p.  1306.  For  an  English  translation  see  the  Kekule  lecture  by  Jepp  in  the 
J.  C.  S.  73,  p.  100  of  Transactions. 

[142] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  15 


only  when  we  take  two  compounds  or  classes  of  compounds  out 
of  their  natural  surroundings  and  contrast  them  by  ignoring  the 
intervening  links.  In  an  age  of  evolution  such  a method  of 
procedure  is  as  fundamentally  wrong  in  chemistry  as  it  is  in 
biology. 


[143] 


A PROPOSED  BASIS  FOR  THE  RATIONAL  CLASSI- 
FICATION OF  CARBON  COMPOUNDS 


CLASSIFICATION  OF  THE  HYDROCARBONS 

Assuming  the  tetra-valence  of  the  carbon  atom,  there  is  but 
one  hydrocarbon  in  which  all  four  of  the  affinities  of  the  carbon 
atom  can  be  saturated  by  hydrogen.  The  four  affinities  may  be 
indicated  in  the  plane  of  the  printed  page  by  four  lines  in  the 

I 

following  manner:  — C — . If  these  affinities  are  saturated  by 

hydrogen  we  get  the  formula  for  methane  or  marsh  gas,  CH4  or 
H 

H — C — H.  In  place  of  saturating  these  four  affinities  with  hy- 
H 

drogen,  or  e.  g.,  with  halogen  or  oxygen,  it  may  be  assumed  that 
one  or  more  may  be  satisfied  by  the  same  number  of  valencies 
of  other  carbon  atoms.  Assuming  for  the  present  that  the  car- 
bon atom  be  united  with  other  carbon  atoms  by  single  affinities 
only,  we  get  the  following  carbon  nuclei  with  their  free  affinities: 


18 


BULLETIN  OP  THE  UNIVERSITY  OP  WISCONSIN 


If  these  free  affinities  are  now  satisfied  by  hydrogen,  the  fol- 
lowing hydrocarbons  result: 


H H 

I I 

H— C— C— H 

I I 

H H 


H H H 

I I I 

H— C— C— C— H 

III 

H H H 


H H H H 

I I I I 

H— C— C— C— C— H 

-Mil 

H H H H 


It  will  be  seen  at  once,  that  each  carbon  atom  is  united  with 
two  hydrogen  atoms,  and  that  the  two  end  carbon  atoms  have  a 
third  affinity  satisfied  by  hydrogen.  For  n carbon  atoms  there  are, 
therefore,  2n  + 2 hydrogen  atoms  in  each  molecule.  Hence, 
the  general  formula  for  these  and  like  hydrocarbons  will  be 
CnH2n+2-  Having  assumed  a tetra- valence  for  the  carbon  atom 
this  will,  therefore,  be  the  limit  series  of  hydrocarbons  ( Grenz - 
kohlenwasserstojje) . We  can  imagine  but  one  such  series  and 
only  one  is  known. 

If  in  place  of  uniting  two  carbon  atoms  of  the  same  molecule 
by  a single  bond,  we  imagine  them  united  by  two  bonds  the  fol- 
lowing carbon  nuclei  will  result: 


\ / \ I I 

c=c  c=c— c— 

/ V / I 


\ I 


/ 


c=c— c— c— 


If  the  free  affinities  be  now  satisfied  by  hydrogen  atoms  the 
following  hydrocarbons  are  obtained: 


H H 

\ / 

C=C 

/ \ 

H H 


H H H 

\ I I 

C=C — C — H 

/ I 

H H 


H H H H 

\ I I I 

C=C— C— C— H 

/ I I 

H H H 


The  addition  of  the  carbon  and  hydrogen  atoms  in  each  mole- 
cule will  show  that  these  hydrocarbons  contain  two  hydrogen 
atoms  less  than  the  hydrocarbons  with  the  same  number  of  car- 
bon atoms  first  developed.  Their  general  formula  will,  there- 
fore, be: 


CnH2n  + 2 — H2  = CnH2n. 
[146] 


KREM3RS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  19 


Hence  we  can  derive  the  hydrocarbons  of  the  formula 
CnH2n  from  the  hydrocarbons  of  the  formula  CnH2n-f-2  by  the  ab- 
straction of  two  hydrogen  atoms. 

This  abstraction  of  hydrogen  atoms  may  take  place  first  of  all 
in  connection  with  neighboring  carbon  atoms.  Thus 


ch3 

ch2— 

CH2 

1 

will  yield 

1 

or 

II 

ch. 

ch,— 

ch2 

ch3 

ch,— 

ch2 

1 

1 

II 

CH, 

l 

will  yield 

CH— 

or 

CH 

1 

ch3 

| 

ch, 

j 

CH, 

ch3 

ch,— 

CH, 

1 

1 

II 

ch2 

1 

will  yield 

CH— 

1 

or 

CH 

1 

ch, 

ch2 

CH, 

1 

ch, 

j 

ch, 

j 

CH, 

CH, 

l 

CH3 

1 

CH— 

CH 

or 

1 

or 

II 

CH— 

1 

CH 

ch3 

| 

CH, 

ch3 

CH— 

CH, 

1 

1 

II 

ch,— ch 

will  yield 

ch,— c— 

or 

ch3— c 

j 

ch3 

1 

ch3 

1 

CH, 

These  hydrocarbons  are  identical  with  those  derived  by  the 
previous  method. 


[147] 


20 


BULLETIN  OB  THE  UNIVERSITY  OB  WISCONSIN 


Secondly,  the  two  hydrogen  atoms  may  be  abstracted  from 
carbon  atoms  that  are  not  neighboring  but  have  one  other  car- 
bon atom  intervening.  In  that  case 


ch3 

ch2— 

ch2 

1 

ch2 

will  yield 

1 

ch2 

or 

dH2— ch5 

ch3 

ch2— 

ch3 

ch2— 

ch2 

1 

ch2 

ch2 

1 

will  yield 

1 

or 

/ \ 

ch2 

CH— 

CH CH2 

1 

1 

ch3 

| 

ch3 

CHS 

ch3 

ch2— 

1 

ch2 

1 

ch2 

ch2 

1 

1 

/ \ 

ch2 

will  yield 

CH— 

or 

CH CH2 

1 

ch2 

| 

ch2 

1 

| 

ch2 

ch3 

ch3 

1 

ch3 

If  next  we  allow  two  carbon  atoms  to  intervene  between  the 
carbon  atoms  from  which  the  hydrogen  atoms  are  abstracted 
the  following  cyclic  hydrocarbons  result: 


ch3 

ch2— 

ch2 

| 

ch2 

ch2— ch2 

1 

will  yield 

1 or 

1 1 

ch2 

ch2 

ch2— ch2 

1 

ch3 

1 

ch2— 

ch3 

1 

ch2— 

1 

1 

ch2 

1 

ch2 

ch2— ch2 

ch2 

will  yield 

1 

CH2  or 

I 

1 1 
CH—  CH2 

1 

ch2 

1 

CH— 

1 

ch3 

j 

ch3 

| 

ch3 

etc. 

[148] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  21 


Next  we  may  allow  three,  four  or  more  carbon  atoms  to  in- 
tervene and  cyclic  hydrocarbons  with  five,  six  and  more  members 
to  the  cycle  will  result. 

Proceeding  from  normal  hydrocarbons  of  the  methane  series 
the  following  hydrocarbons  are  obtainable.  The*  cyclic  members 
are  classified  according  to  the  number  of  carbon  atoms  to  the 
cycle  and  are  tabulated  so  as  to  show  the  isomerism  of  the  hy- 
drocarbons with  the  same  number  of  carbon  atoms. 


[149] 


22 


bulletin  of  the  UNIVERSITY  OF  WISCONSIN 


CnH2n-f  2 


ch4 

ch3 

ch2 

1 

II 

ch3 

ch2 

ch3 

1 

ch2 

II 

ch2 

CH 

ch2 

1 

ch3 

1 

CH, 

ch2— ch2 

ch3 

ch2  ch3 

ch2 

1 

II  1 

/ \ 

ch2 

t 

CH  CH 

i II 

CH— CH2 

ch2 

1 

1! 

CH2CH 

| 

CH, 

ch3 

| | 

CH,  CH, 

ch3 

1 

ch2  ch3 

ch2 

ch2 

II  1 

/ \ 

/ \ 

ch2 

1 

CH  CH 

1 II 

CH— CH2 

CH— CH 

ch2 

1 

1 II 

ch2ch 

| 

ch2 

| | 
CH,  CH, 

ch2 

1 1 
ch2  ch2 

1 

CH, 

ch, 

ch,  ch, 

ch3 

ch2  ch3  ch3 

ch2 

ch2 

1 

II  1 1 

/ \ 

/ \ 

ch2 

1 

CH  CH  CH2 

1 II  1 

CH,CH  CH 

1 I il 

CH— CH2 

CH— CH 

ch2 

1 

| 

ch2 

1 

CH2  CH, 

ch2 

1 

1 1 II 

CH2  CH2  CH 

ch2 

CH, 

ch2 

1 

1 1 1 
ch2  ch2  ch2 

I 

CH, 

ch3 

1 1 1 

CH,  CH,  CH, 

etc. 

etc. 

1150] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  23 


Cn  H2n 


CHj— CH2 

ch2— ch2 

CH2— CH2 

1 1 

CH—  CH2 

1 

ch3 

ch2— ch2 

1 >CH‘ 
ch2— ch2 

CH2— CH2 

1 1 

CH—  CH2 

ch2  ch2— ch2 

1 1 1 

CH3  CH  — CH 

1 1 

CH3  CH3 

ch2— ch2  ch2— ch2 

\ch,  / \ 

CHi  CRi 

CH  — CH2  \ / 

| ch2— ch2 

CH3 

A second  dimethyl  cyclobutane  has  been  omitted  for  want  of 
space. 


U51] 


24 


bulletin  of  the  university  OF  WISCONSIN 


Whereas  of  the  formula  of  saturation  C2nH2n_i-2  but  one  series 
of  hydrocarbons  is  possible,  and  representatives  of  but  one  series 
are  known;  of  the  formula  of  saturation  CnH2n,  one  chain  series 
and  an  indefinite  number  of  cyclic  series  can  be  developed.  Repre- 
sentatives of  the  chain  series  and  of  four  of  the  cyclic  series  are 
known.  Derivatives  of  still  another  series  with  seven  carbon 
atoms  to  the  cycle  are  likewise  known. 

The  names  of  the  normal  chain  hydrocarbons  and  initial  mem- 
bers of  the  cyclic  series  are  commonly  given  in  accordance  with 
the  principles  of  the  Geneva  Congress. 

If  we  now  proceed  one  step  farther  and  abstract  two  more 
hydrogen  atoms  we  arrive  at  the  formula  of  saturation  CnH2n_  2. 
Under  this  formula  two  unsaturated  chain  series  and  the  following 
unsaturated  monocyclic  series  and  saturated  dicyclic  series  may 
be  developed. 

In  the  following  tabulations  some  of  the  isomeric  forms  have 
been  omitted  for  want  of  space  on  the  page  on  which  they  be- 
longed. All  isomeric  forms  with  the  double  bonds  in  the  side 
chains  have  been  omitted  for  the  same  reason.  These  tables 
have  been  compiled,  not  with  any  idea  of  completeness,  but 
rather  for  the  purpose  of  affording  a convenient  oversight  such 
as  seems  necessary  for  a proper  grasp  of  the  situation. 


[152] 


KRAMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  25 


CnH2n — 2 


F 

F F 

CH 

III 

CH 

CH 

III 

C 

l 

1 

ch. 

CH 

ch3 

ch2 

III 

1 

II 

c 

1 

c 

III 

c 

CH 

1 

ch2 

CH 

1 

1 

II 

CH, 

CH, 

ch2 

CH 

ch3 

ch2 

ch2 

III 

1 

II 

II 

c 

c 

CH 

CH 

1 

III 

1 

1 

ch2 

1 

c 

CH 

ch2 

1 

II 

1 

ch2 

ch2 

CH 

CH 

1 

1 

1 

II 

ch3 

ch3 

ch3 

ch2 

CH 

ch3  ch3 

ch2 

ch2 

ch2 

CH, 

III 

1 1 

II 

II 

1 

1 

C 

c ch2 

CH 

CH 

CH 

CH 

1 

III  1 

1 

1 

II 

II 

ch2 

1 

c c 

1 III 

ch2  c 

CH 

II 

CH 

ch2 

1 

ch2 

CH 

1 

1 

ch2 

1 

CH 

1 

ch2 

CH 

1 1 

1 

II 

1 

II 

ch2 

ch2  ch2 

ch2 

CH 

CH 

CH 

1 

1 1 

1 

1 

II 

1 

ch3 

CHa  CH3 

CH, 

ch3 

ch2 

CH, 

[153] 


26 


BULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


CnH2n — 2 


r a 


/CH 

ch2|| 

\CH 


/CH 

ch2|| 

\c 


/CH 
CH  || 
\CH 


ch3 

ch3 

/CH 

/CH 

ch3 

/CH 

CH2|| 

CH  || 

1 

CH  || 

\c 

1 \CH 

/C 

1 \c 

1 

ch2|| 

1 

ch2 

ch2 

\c 

ch3ch3 

ch3 

| 

ch3 

1 

ch3 

/CH 

/CH 

/CH 

/CH 

ch3 

CH, 

CH, 

ch2  II 

CH2|| 

CH  || 

CH  || 

1 

1 

1 

\c 

\c 

| \CH 

| \CH 

/C 

/C 

/C 

1 

1 

1 

1 

CH2|| 

CH  || 

CH  || 

ch2 

CH— CH3 

1 

ch2 

CH— CH3 

\c 

|\CH 

Pi 

ch2 

ch3 

1 

ch2 

| 

CH, 

ch2 

ch2 

j 

ch3ch, 

1 

CH, 

1 

CH, 

1 

CH, 

CH, 

[154] 


KRAMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  27 


CnH2n — 2 

r a 


CHj— CH 

I II 

CH2— CH 


CH2— CH 

I II 

ch2 — c 

I 

ch3 


CH2— CH 

I II 

CH—  CH 

I 

CH, 


CH2— CH 

! II 

CH2— c 

I 

ch2 

I 

CH* 


CH2— CH 

I II 

CH  — CH 

I 

ch2 

I 

CH, 


CH, 


CH2— C 

I II 

CH2— c 


I 

CH, 


CH2— CH 

I II 

CH  — C 

I I 

CH,  CH, 


CH, 

I 

CH  — CH 

I II 

CH2— c 

I 

CH, 


[155] 


28 


bulletin  of  the  university  OF  WISCONSIN 


CnH2n — 2 


r a 

■ 

/CH2— ch 

CHj  || 

\CH2— CH 

/CH2— CH  /CH2— CH  /CH2— CH 

CH2  II  CH2  II  CH  II 

XCH*— C \CH—  CH  I \CH2— CH 

1 1 1 

CH3  CH»  CHj 

/CH2 — CH2\ 

ch2  ch2 

\CH  = CH/ 

[156] 


kremers — the  classification  of  carbon  compounds  29 


CnH2n — 2 


A A 


CH2— CH 


/I 


CH  — CH2 


CH2— CH 

I /I 


CH  — CH 


CHg 


CH2— CH 

U-1 


c — ch2 


ch3 


CH, 

CH, 

CH, 

CH2— CH 

CH2— CH 

| 

CH2— c 

| 

CH  — CH 

| 

CH2— c 

1 /I 

1/1 

1 /I 

1 /! 

1/1 

CH  — CH 

1 

c — ch2 

1 

CH  — CH 

1 

CH2— CH 

c — ch2 

ch2 

1 

ch2 

CH, 

| 

CH, 

CH, 

1 

CHg 

1 

CH, 

[157] 


30 


bulletin  of  the  university  OF  WISCONSIN 


CnH2n — 2 


A A 


/CH— CHj 

CH2|  | 

\CH— CH2 

/CH— CH2  /CH— CH2  /CH— CH2 

CH2|  1 CH,|  1 CHI  1 

\CH— CH  \C  — CH2  INCH— CH2 

1 1 1 

CH,  CH,  CH, 

/CH— CH2\  CH2— CH— CH2 

ch2  1 ch2  I 1 

\CH— CH2/  CH2— CH— CH2 

[158] 


krkmers — the:  classification  of  carbon  compounds  31 


It  is  not  necessary  to  carry  the  details  of  this  process  any 
farther,  if  we  but  realize  the  important  conclusion  that  can  be 
derived  from  the  few  instances  cited,  viz.,  that  the  structural 
equivalent  of  two  hydrogen  atoms  is  either  a double  bond  or  a 
cycle,  also  that  in  place  of  two  double  bonds  we  may  have  still 
another  structural  equivalent,  the  treble  bond. 

Bearing  this  in  mind,  we  can  readily  classify  under  each  formula 
of  saturation  the  groups  of  series  of  hydrocarbons.  In  the  follow- 
ing table  these  groups  are  indicated  with  the  use  of  the  following 
symbols : 


F — double  bond 
A = cycle 
F — treble  bond. 


CnH2n  + 2 

c„h2d 

^n^2n_2 

CnH2n_4 

r 

F F 

F F F 

A 

FA 

A A 

F 

F F A 

F A A 
AAA 

F F 

F A 

CnH2D_6 

r F F F 

F F F A 

F F A A 
r AAA 
AAA  A 

C„H2n_8 

^n  ^2n  — 10 

^2n  — 12 

7 F 

6 r and  1 A 
5 and  2 A 

etc. 

F F 
F F F 
F F A 
F A A 


Hence,  the  hydrocarbons  may  be  rationally  classified 
Firstly,  According  to  their  degree  of  saturation; 
Secondly,  According  to  their  chain  or  cyclic  character; 
Thirdly,  According  to  the  number  of  carbon  atoms. 

[159] 


32 


BULLETIN  OB  THE  UNIVERSITY  OF  WISCONSIN 


CLASSIFICATION  OF  THE)  SUBSTITUTION  PRODUCTS 
OF  THE  HYDROCARBONS 

Having  outlined  very  briefly,  the  principles  that  should  govern 
us  in  a rational  classification  of  the  basal  carbon  compounds, 
the  hydrocarbons,  we  are  now  prepared  to  classify  their  substi- 
tution products. 

In  the  large  number  of  known  hydrocarbons  and  in  the 
thousands  of  unknown  but  possible  hydrocarbons  we  have,  in 
addition  to  carbon  atoms  that  have  their  four  affinities  saturated 
exclusively  with  the  affinities  of  other  carbon  atoms,  the  follow- 
ing three  simple  hydrocarbon  groups: 

— CH3>  the  univalent  methyl  group 
= CH2,  the  bivalent  methylene  group 
=CH,  the  trivalent  methenyl  or  formyl  group 

As  has  already  been  pointed  out,  methane  constitutes  the 
single  exception  to  this  rule.  Hence  its  substitution  products  or 
derivatives  differ  somewhat  from  the  analogous  derivatives  of 
other  hydrocarbons. 

Inasmuch  as  we  are  going  to  regard  all  carbon  compounds  as 
substitution  products,  direct  or  indirect,  of  the  underlying  hy- 
drocarbons, all  direct  substitution  must  take  place  in  connection 
with  one  of  these  three  simple  groups.  This  suggests  at  once 
one  of  the  basal  ideas  of  classification. 

Even  more  fundamental,  however,  is  the  conception  of  how 
often  substitution  has  taken  place.  Inasmuch  as  it  is  the  uni- 
valent hydrogen  of  the  hydrocarbon  that  is  replaced  step  by 
step,  the  unit  of  substitution  must  be  a univalent  atom  or  radicle. 
Accordingly  we  distinguish  between  mono-,  di-,  tri-,  tetra-,  etc., 
substitution  products.  This  is  done  irrespective  of  the  substitut- 
ing element  or  radicle. 

In  order  to  illustrate  the  principles  involved,  substitutions 
with  univalent  elements  also  with  the  univalent  hydride  radicles 
of  divalent  and  trivalent  elements  will  be  effected. 


[160] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  33 


Halogen  Substitution  Products 

For  substitution  with  a univalent  element,  the  halogens  are 
best  adapted.  Of  mono-halogen  substitution  products  there  must 
be  three  types,  since  all  three  simple  hydrocarbon  groups  contain 
at  least  the  one  hydrogen  atom  necessary  for  mono-substitution. 

— CH3  — ch2x 

=CH2  =CHX 

=CH  =CX 

Whereas  mono-substitution  can  take  place  only  in  connection 
with  one  carbon  atom,  di-substitution  can  take  place  in  connec- 
tion with  either  one  or  two  carbon  atoms.  If  it  takes  place  in 
connection  with  the  same  carbon  atom,  two  types  of  di-substitu- 
tion products  are  possible,  and  only  two,  for  but  two  of  the  three 
simple  hydrocarbon  groups  contain  the  requisite  two  hydrogen 
atoms,  viz. 

— CH3  — chx2 

=CH2  =CX2 

Tri-halogen  substitution  can  take  place  in  connection  with  one, 
two  or  three  carbon  atoms.  If  it  takes  place  in  connection  with 
the  same  carbon  atom,  but  one  type  of  tri-halide  is  possible,  since 
but  one  of  the  three  simple  hydrocarbon  groups  contains  the 
requisite  number  of  hydrogen  atoms  to  admit  of  tri-substitution, 
viz. 

— CH3  — CX3 

With  the  exception  of  methane,  which,  with  its  derivatives,  as 
has  already  been  pointed  out,  must  occupy  an  exceptional  posi- 
tion in  any  rational  classification,  tetra-substitution  cannot  take 
place  in  connection  with  one  and  the  same  carbon  atom.  Hence 
the  possibilities  of  substitution  in  connection  with  one  and  the 
same  carbon  atom  are  exhausted  with  tri-substitution.  Substi- 
tution in  connection  with  different  carbon  atoms  will  be  con- 
sidered later.  Suffice  it  for  the  present  to  state  that  no  new 
types  are  created  by  substitution  in  connection  with  different 
carbon  atoms.  The  isomerism  thus  produced  is  one  of  position. 

[161] 


34 


bulletin  op  the  university  OP  WISCONSIN 


The  influence  of  position  on  the  structure  of  a molecule  is  a study 
by  itself  and  should  not  be  confounded  with  that  of  simple  types. 

Hydroxy  Substitution  Products 

Among  the  divalent  elements  of  organic  chemistry,  oxygen  is 
undoubtedly  the  most  important.  Inasmuch  as  the  unit  of  sub- 
stitution in  the  underlying  hydrocarbon  is  the  univalent  hydro- 
gen atom,  it  would  not  be  rational  to  replace,  step  by  step,  hy- 
drogen atoms  by  their  oxygen  equivalents.  Substitution,  how- 
ever, can  be  rationally  effected  by  a univalent  oxygen-hydrogen 
radicle,  such  as  we  possess  in  the  hydroxy  or  hydroxyl  group,  viz. 
the  (— O— H). 

The  simplest  kind  of  hydroxy  substitution  product  will  na- 
turally be  the  mono  hydroxide.  As  of  mono-halides,  and  for  the 
same  reason,  there  are  three  types  of  mono-hydroxides  or  alco- 
hols. They  are  represented  by  the  following  type  formulas: 

— CHj  — CH2OH 

=CH2  =CHOH 

=CH  ~COH 

Of  di-substitution  products,  in  which  the  di-substitution  has 
taken  place  in  connection  with  the  same  carbon  atom,  two  types 
of  dihydroxides,  or  glycols,  are  possible,  viz. 

— CH3  — CH(OH)2 

=CH2  =C(OH)2 

Of  tri-hydroxides,  in  which  all  three  hydroxy  groups  are  con- 
nected with  the  same  carbon  atom,  but  one  type  is  possible,  viz. 

— CHS  — C(OH)3 

Such  a tri-atomic  alcohol  in  which  all  three  hydroxy  groups  are 
connected  with  the  same  carbon  atom  is  known  as  an  ortho  acid. 

It  is  a well  known  fact  in  organic  chemistry  that,  whenever 
two  or  more  hydroxy  groups  are  connected  with  the  same  carbon 
atom,  a tendency  manifests  itself  to  split  off  the  elements  of  a 
molecule  of  water,  a tendency  readily  interpreted  with  the  aid  of 
the  thermochemical  equation  of  water. 

[162] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  35 


The  two  glycols,  also  the  ortho  acid,  are  subject  to  such  de- 
hydration as  indicated  by  the  following  type  formulas: 


/H  /H 

— C-OH  — H20=  — C=0 

\OH 


Aldehyde-yielding 

glycol 

/OH 
— C 
\OH 


Ketone-yielding 

glycol 


/OH 
' — OH 
\OH 


— H20= 


— h2o= 


Aldehyde 


=c=o 


Ketone 


/OH 

-C= 


Ortho  acid 


Meta  acid 


There  are,  therefore,  as  many  as  nine  simple  types  of  oxygen 
substitution  products:  six  hydroxy  substitution  products,  which, 
together  with  their  dehydration  products  are  herewith  tabulated. 


Hydrocarbon  Mono- 
groups hydroxides  Dihydroxides 


Trihydroxides 


/H 

— ch3  — c— h 

\OH 

Methyl Primary . 

alcohol 


/H 

=ch2  =c— oh 

Methylene  Secondary 
alcohol 


=CH  =COH 

Methenyl Tertiary 

alcohol 


/H  /OH 

— C— OH  — C— OH 

\OH  \OH 

.Aldehyde Ortho  acid 

yielding 

glycol 

/H  /O 

— c — c 

M)  \OH 

Aldehyde Meta  acid 


/OH 

=C 

\OH 

Ketone- 

yielding 

glycol 

=c=o 

Ketone 


[163] 


36 


BULLETIN  OE  THE  UNIVERSITY  OE  WISCONSIN 


Amido  Substitution  Products 

Of  the  trivalent  elements,  nitrogen  is  unquestionably  the  most 
important  in  organic  chemistry.  However,  it  is  not  practicable 
to  substitute,  even  in  a theoretical  way,  one-third  and  two-thirds 
of  a nitrogen  atom  for  one  and  two  hydrogen  atoms,  respectively. 
The  simplest  univalent  nitrogen-hydrogen  radicle,  the  amido  or 
amino  group,  however,  may  replace  the  hydrogen  of  an  under- 
lying hydrocarbon.  As  a matter  of  fact,  it  is  with  compounds 
such  as  these  that  the  organic  chemist  has  to  deal.  Hence  the 
nitrogen  derivatives  can  best  be  studied  as  amido  substitution 
products  and  their  deammoniated  compounds. 

As  with  the  halides  and  hydroxides,  the  monamides  come  first. 
Also,  as  with  the  mono-halides  and  mono-hydroxides,  there  are 
three  types  of  monamides,  according  to  the  replacement  of  a 
methyl,  methylene,  or  methenyl  hydrogen  atom,  as  indicated 
by  means  of  the  following  formulas: 

— CH3  — ch2nh2 

=CH2  =CHNH 

=CH  =CNH2 

In  connection  with  the  diamines  we  must  again  distinguish 
between  those  diamides  in  which  the  two  amido  groups  are  con- 
nected with  the  same  carbon  atom,  and  those  in  which  they  are 
connected  with  two  carbon  atoms.  The  former  only  are  here 
considered.  Of  these  there  are  again  two  types  as  of  the  cor- 
responding di-halides  and  di-hydroxides,  viz. 

/H  /H 

— C-H  — C-NH2 

\H  \NH2 

p/H  _r/NH2 

'~\H  ~l\NH2 

In  like  manner  as  the  corresponding  di-hydroxides  readily 
split  off  the  elements  of  a molecule  of  water,  so  the  diamides, 
(though  with  less  readiness)  split  off  the  elements  of  a molecule 
of  ammonia,  yielding  the  corresponding  imides  as  indicated  by 
the  following  formulas: 

/H  /H 

— C-NH2  — NH3=  — C=NH 

\nh2 

=c<nS:  -nh*=  =c=nh 

[164] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  37 


These  two  imides  correspond  to  the  aldoximes  and  ketoximes, 
respectively. 

Of  the  triamides,  in  which  the  three  amido  groups  are  con- 
nected with  the  same  carbon  atom,  but  one  is  derivable,  viz.,  that 
from  the  methyl  group,  which  is  the  only  simple  hydrocarbon 
group  containing  the  requisite  number  of  hydrogen  atoms.  By 
splitting  off  ammonia  it  may  yield  first  the  amidine,  and  then 
the  nitrile,  as  indicated  by  the  following  formulas: 


/NH2 

— c-nh2 
\nh2 

— NH,= 

[ k 

\ 

[ aw 

Triamide 

Amidine 

p/NH2 

l\nh 

— nh3= 

A 

I 

Amidine 

Nitrile 

In  the  following  table  the  simple  types,  ten  in  all,  of  the  amido 
substitution  products  and  their  deammoniated  compounds  are 
given : 


Hydrocarbon  Monamides 
groups 


/H 

-C-H 

\H 


/NH2 

-C-H 

\H 


p/H  _p/NH2 

~ C\H  '\H 

=CH  ==CNH2 


Diamides 


Triamides 


/NH2 
— C-NH2 
\H 


/NH2 


— c-nh2 
\nh2 


— c 


/NH 

\H 


n/NH 

l\NH, 


=C=NH 


The  possibility  of  splitting  off  ammonia  in  a different  manner 
will  not  be  discussed  at  this  point. 


Other  Substitution  Products 

With  the  halogen  substitution  products,  we  have  disposed,  with 
the  exception  of  manganese,  of  the  known  elements  of  the  sev- 
enth group  of  the  periodic  system,  i.  e.,  so  far  as  the  simple  ele- 

[165] 


38 


BULLETIN  OB  THE  UNIVERSITY  OR  WISCONSIN 


mental  substitution  products  are  concerned.  These  constitute 
by  far  the  bulk  of  halogen  organic  compounds. 

Like  the  oxygen  derivatives,  so  the  sulphur,  selenium,  and 
tellurium  derivatives  can  be  derived  by  the  substitution  of  their 
simple  hydride  groups  for  hydrogen,  and  the  subsequent  split- 
ting off  of  sulphuretted  hydrogen,  etc.  Such  compounds  as  sul- 
phates, sulphites,  etc.,  are  easily  derived  as  are  the  corresponding 
derivatives  of  the  inorganic  acids. 

Analogous  to  the  amides  are  the  phosphines,  arsines,  etc.  What 
has  been  said  of  the  sulphates  applies  also  to  phosphates,  arse- 
nates, etc. 

We  now  arrive  at  the  fourth  group  of  the  periodic  system. 
The  typical  organic  element  of  this  group  is  carbon.  Its  simplest 
univalent  hydride  group  is  the  methyl  group.  By  the  substitution 
of  this  methyl  group  for  a hydrocarbon  hydrogen  we  obtain  a 
homologue  of  the  hydrocarbon  in  question.  This  brings  us  back 
to  the  hydrocarbons. 

The  classification  of  substitution  products  obtained  by  the  sub- 
stitution of  elements  of  groups  three,  two,  one,  and  eight,  need 
not  concern  us  at  present. 

Genetic  Relationship  or  Types 

We  have  thus  far  reduced  the  large  bulk  of  simple  carbon  com- 
pounds to  relatively  few  types.  While  it  should  always  be  re- 
membered that  the  properties  of  a compound  are  functions  of  its 
structure,  and  that  the  structure  of  a compound  implies  more 
than  the  peculiar  characteristics  of  the  type  or  types  to  which  it 
belongs,  yet  the  type  is  of  fundamental  importance.  It  is  essen- 
tially the  same  irrespective  of  degree  of  saturation,  of  chain  or 
cyclic  character,  and  of  the  number  of  carbon  atoms.  Differences 
are  primarily  differences  of  degree.  All  of  these  factors,  how- 
ever, exert  a modifying  influence,  as  does  also  the  piling  up  of  a 
number  of  the  same  type  groups  within  the  same  molecule. 

These  are  matters  to  be  brought  out  later,  at  least  in  so  far  as 
they  exert  an  influence  on  the  mode  of  classification.  For  the 
present,  however,  we  are  concerned  with  simple  types  only. 

The  advantages  of  the  system  of  classification  thus  far  out- 
lined are  those  of  simple  logical  questions  and  answers,  based 

[166] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  39 


on  a definition  that  foreshadows  the  questions.  Organic  chem- 
istry being  defined  as  the  chemistry  of  the  hydrocarbons  and  their 
substitution  products,  the  latter  are  naturally  classified  into 
mono-,  di-,  tri-,  etc.,  substitution  products,  that  is,  according  to 
the  number  of  times  substitution  has  taken  place,  irrespective 
of  the  substituting  element  or  radicle.  Taking  into  consideration 
that  there  are  three  simple  hydrocarbon  groups  of  which  all  hy- 
drocarbons are  made  up,  it  follows  that  there  must  be  three  types 
of  mono-substitution  products.  For  the  same  reason  there  are 
two  types  of  di-substitution  products,  and  but  one  of  tri-substi- 
tution products  in  which  substitution  has  taken  place  in  connec- 
tion with  the  same  carbon  atom.  If  substitution  takes  place  in 
connection  with  different  carbon  atoms,  no  new  simple  types, 
as  has  already  been  pointed  out,  are  formed. 

A system  of  classification  based  on  rational  questions  and  an- 
swers should  certainly  be  a gain  over  a mode  of  classification  based 
on  several  historical  systems.  While  different  points  of  view 
are  not  only  an  advantage,  but  a necessity,  in  the  study  of  chem- 
istry, in  the  classification  of  compounds  a Unitarian  point  of  view 
should  be  maintained  if  possible. 

But  even  such  a gain  might  not  be  worth  the  trouble  involved 
in  a change  if  the  system  proposed  did  nothing  more  than  to  effect 
a systematic  pigeonholing  of  chemical  compounds.  A rational 
classification  based  on  chemical  structure,  and  on  the  theory  that 
the  properties  of  a chemical  compound  are  functions  of  its  struc- 
ture, must  accomplish  much  more.  It  must  bring  out  the  genetic 
relationship  of  the  different  types. 

This  genetic  relationship  can  be  brought  out  in  several  ways. 
Suffice  it  for  the  present  to  bring  out  the  relationship  between 
the  simple  underlying  hydrocarbon  groups  and  the  types  of  the 
three  classes  of  mono-,  di-,  and  tri-valent  elements  utilized  thus 
far  for  purposes  of  illustration.  This  relation  can  best  be  re- 
vealed with  the  aid  of  tabulated  structural  formulas. 


[167] 


40 


BULLETIN  of  THE  UNIVERSITY  OF  WISCONSIN 


Types  of  Mono-substitution  Products 


Hydrocarbon 

groups 

— CHS 

=CH2 

=CH 


Halides 
— CH2X 
=CHX 
=CX 


Hydroxides 
— CH2OH 
=CHOH 
=COH 


Amides 
— CH2NH2 

=chnh2 

=cnh2 


Adopting  a style  of  nomenclature  that  was  originally,  so  far 
as  the  compounds  here  involved  are  concerned,  applied  to  the 
hydroxides  or  alcohols,  we  distinguish  the  three  types  by  des- 
ignating them  primary,  secondary,  and  tertiary,  respectively. 
For  a long  time  this  mode  of  distinction  has  also  been  applied  to 
the  corresponding  halides,  but  not  to  the  corresponding  amides. 
It  is  right  here  that  the  irrationality  of  mixing  systems  of  classi- 
fication and  nomenclature  is  keenly  felt.  For  our  purposes  we 
shall,  therefore,  adhere  rigidly  to  what  appears  to  be  the  only 
rational  solution  of  this  confused  condition.  A primary  mono- 
substitution product  is  a compound  in  which  this  substitution 
has  taken  place  in  connection  with  a methyl  group  of  a hydro- 
carbon. A secondary  compound,  one  in  which  the  substitution 
has  taken  place  in  connection  with  a methylene  group,  and  a 
tertiary  compound,  one  in  which  it  has  taken  place  in  connection 
with  a methenyl  group.  Or  in  other  words,  using  the  structural 
groups  tabulated  above,  a primary  alcohol  is  a compound  char- 
acterized by  a — CH2OH  group;  a secondary  halide,  a compound 
characterized  by  a =CHX  group,  a tertiary  amide  a compound 
characterized  by  a ==CNH2  group. 

If  it  be  continually  borne  in  mind  that  these  group  formulas, 
like  the  complete  formulas  of  chemical  compounds,  are  but  the 
chemical  shorthand  for  the  properties  involved,  no  harm  can 
result.  It  may  not  be  amiss,  therefore,  to  review  a few  of  these 
properties,  well  known  as  they  are.  Using  the  most  general 
expressions,  they  can  be  represented  by  the  equations: 

R'H  + X2  = R'X  4-  HX 
R'X  + M'OH  = R'OH  + M'X 
R'X  + HNH2  = R'NH2  + HX 


[168] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  41 

Thus  it  is  possible  to  pass  by  simple  reactions  from  the  hydro- 
carbon to  the  halide,  and  from  the  halide  to  the  hydroxide  and 
amide.  It  is  also  possible  to  reverse  the  order,  e.  g.,  from  the 
hydroxide  to  the  halide: 

R'OH  + HX  = R'X  + H20; 

or  from  the  amide,  through  the  diazo  compound,  to  either  the 
alcohol 

R'NH2  + ONOH  = R'N  = NOH  + H20 
R'N  = NOH  = R'OH  + N2; 

or  by  first  converting  the  diazo  compound  into  diazo-halide,  to 
the  simple  halide 

R'N  = NX  = R'X  -f  N2. 

Finally  it  is  possible,  by  so-called  inverse  substitution,  to  re- 
duce the  halide  to  the  hydrocarbon: 

R'X  + XH  = R'H  + X2. 

Thus  the  cycle  of  changes  is  completed. 

By  using  the  partly  analyzed  formulas  as  indicated  by  the  type 
formulas  tabulated  above,  it  becomes  apparent  how  a primary 
halide  will  yield  a primary  alcohol,  or  a tertiary  amide  upon  di- 
azotation,  a tertiary  alcohol,  etc.  A host  of  organic  reactions 
can  thus  be  grouped  into  a few  type  reactions  which  follow  from 
the  method  of  classification.  When  such  results  are  possible, 
the  mere  pigeonholing  certainly  can  be  regarded  as  a mere  in- 
cident, though  practically  an  important  one,  in  a system  of  clas- 
sification and  nomenclature. 


Types  of  Di-substitution  Products 


Hydrocarbon 

groups 

Halides 

Hydroxides 

Amides 

/H 
— C-H 
\H 

<_> 

1 

/H 

— C-OH 
\OH 

/H 

— c-nh2 
\nh2 

_C/H 

So 

_C/H 

C\NH 

_C/R 
— C\H 

=c<£ 

_C/°H 

—U\OH 

_r/NH2 

“L\NH2 

= C=0  =c=nh 


=CH 


[169] 


42 


bulletin  of  the  university  OF  WISCONSIN 


Here  again  genetic  relationship  becomes  apparent  as  expressed 
by  such  well-known  reactions  as  the  following: 

R'CHX2  + 2M'OH  = R'CHO  + H20  + 2M'X 
R'2CX2  -f  2M'OH  = R'2CO  -f  H20  + 2M'X 

As  is  well  known  these  reactions  also  are  reversible: 


R'CHO  4-  X2PX3  = R'CHX2  + OPX, 
R'2CO  + X2PXa  = R'2CX2  + OPX3 


If  in  place  of  the  imides,  resulting  upon  deammoniation  from 
the  diamides,  we  substitute  their  hydroxy  or  oxy  derivatives,  the 
oximes,  the  genetic  relationship  between  aldehydes  and  ketones, 
on  the  one  hand,  and  their  respective  oximes,  on  the  other  hand, 
is  readily  expressed  by  the  following  general  equations: 

R'c<o  + h2noh  = R'c<”oh  + h2o 

Aldehyde  Aldoxime 


R2'C  = 0 + H2NOH  = R'2C  = NOH  + H20 
Ketone  Ketoxime 


Whereas  the  oximes  result  upon  condensation,  upon  hydrolysis 
they  may  be  caused  to  resolve  into  their  components,  hydroxyl- 
amine  and  either  aldehyde  or  ketone. 

^ ^\NOH  4-  = ^ **"  H2NOH 

Aldoxime  Aldehyde  Hydroxylamine 

R'2C  = NOH  4-  OH2  = R'2C  = 0 4-  H2NOH 

Ketoxime  Ketone  Hydroxylamine 


Types  of  Tri-Substitution  Products 


Hydrocarbon 

groups 


/H 


— C-H 
\H 


Halides 


/X 


— c-x 
\x 


Hydroxides 


/OH 
— C-OH 
\OH 

~c<r0H 


Amides 


/NH2 
— C-NH2 

\nh2 


— C=N 


— CH 


[170] 


kremers — the  classification  of  carbon  compounds  43 


A number  of  well-known  reactions  might  be  cited  to  point 
out  the  genetic  relationship  indicated  by  the  above  group  for- 
mulas. A few  may  suffice. 

Under  certain  conditions  all  three  hydrogen  atoms  of  a methyl 
group  can  be  replaced  readily  by  halogen: 

R'COCHs  + X*  = R'COCX3  + 3HX. 

The  above  tri-halide  is  readily  hydrolized  to  methenyl  or 
formyl  tri-halide  (chloroform,  bromoform  and  iodoform). 


R'C  = 0 

CX* 

M'O 

H 

R'C  = 0 

CX8 

\ 

1 

OM' 

H 

The  trihalide  thus  resulting  can  be  converted  either  into  the 
tri-hydroxide  or  ortho  acid  and  its  dehydration  product,  the 
meta  acid,  or  through  the  triamide  into  the  corresponding  amidine 
and  nitrile. 


H 

r^X  + M'OH  = 
^X  + M'OH 
'X  + M'OH 
Tri-halide 


/H 

r/x  + H NH2  = 
C\X  + H NH2 
NX  + H NH2 
Tri-halide 


/H 

<4gg  + 

3MX 

'oh 

Tri-hydroxide 
or  Ortho  acid 

c/oH 
'‘yOH  = 

T)H 

/H 

C-OH  + 

%o 

Meta  acid 

h2o 

/H 

r/NH2  , 

cVnh2  + 

nNH2 

Tri-amide 

3HX 

/H 

n/NHj  = 

lvnh2 

nNH2 

/H 

C-NH2  + 
\NH 

Amidine 

nh2 

/H 

C-NH2  = 
\NH 

c<«  + NHa 
Nitrile 

[171] 


44 


BULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


The  nitrile  in  turn  can  be  hydrolyzed  to  the  acid  through  the 
acid  amide: 

sTT  /H 

+ OH2  = C— NH2 
^ \0 

Nitrile  Acidamide 

/H  /H 

c-nh2  + oh2=c-o— nh4 

\o  \o 

Ammonium  salt  of  acid 

Other  genetic  relationships,  as,  e.  g.,  between  mono-,  di-,  and 
tri-,  substitution  products,  can  be  brought  out.  Thus  the  stu- 
dent in  organic  chemistry  is  taught  that  the  difference  between 
a primary,  secondary  and  tertiary  alcohol  consists  in  this,  that 
the  primary  alcohol  can  readily  be  oxidized  to  an  aldehyde  and 
an  acid  with  the  same  number  of  carbon  atoms,  the  secondary 
alcohol  to  a ketone,  and  that  the  tertiary  alcohol  is  not  capable 
of  similar  oxidation.  This  fact  was  first  emphasized  by  Kolbe 
basing  his  structural  notions  on  the  type  carbinol.  Having 
abandoned  the  theory  of  types  to  a large  extent,  the  above  def- 
initions have  largely  lost  their  structural  significance,  at  least 
as  brought  out  in  textbooks.  The  structural  significance  is 
again  emphasized,  but  from  the  Unitarian  point  of  view  of  our 
definition  of  organic  chemistry,  viz.,  that  organic  chemistry  is 
the  chemistry  of  the  hydrocarbons  and  their  substitution  prod- 
ucts. 


[172] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  45 


MULTIPLICATION  OF  TYPES 


Thus  far  only  those  substitution  products  have  been  considered 
in  which  substitution  has  taken  place  in  connection  with  the 
same  carbon  atom.  It  has  already  been  pointed  out  that  sub- 
stitution in  connection  with  different  carbon  atoms  produces  no 
new  types  but  merely  a multiplication  of  types  already  devel- 
oped. This  becomes  apparent  if  we  but  recall  that  with  the 
exception  of  methane  all  hydrocarbons  are  composed,  so  far  as 
substitution  is  concerned,  of  the  three  simple  groups  used  in  de- 
veloping types  thus  far  studied.  This  a priori  reasoning  is  in 
accord  with  the  facts.  A few  relatively  simple  and  well-known 
illustrations  will  clearly  reveal  this. 

Thus,  e.  g.,  glycerin  is  a tri-atomic  alcohol  in  which  the  three 
hydroxy  groups  are  associated  one  with  each  of  the  three  car- 
bon atoms  as  represented  by  the  following  formula  referable  to 
propane. 


ch3 

CH2OH 

1 

ch2 

1 

| 

CHOH 

1 

ch3 

CH2OH 

Propane 

Propane- triol — 1,  2,  3,  or  glycerin 

It  is  twice  a primary  alcohol  and  once  a secondary  alcohol  and 
the  above  chemical  shorthand  expression  is  in  accordance  with 
the  properties  of  this  substance. 

Erythrol  is  a similar  tetratomic  alcohol  and  some  of  its  prop- 
erties find  expression  in  the  formula  of  tartaric  acid  to  which 


it  can  be  oxidized. 

ch3 

ch2oh 

COOH 

I I I 

ch2  choh  choh 

I I I 

ch2  choh  choh 


CHS 

CH2OH 

COOH 

Butane 

Erythrol 

Tartaric  acid 

[173] 

46 


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With  the  multiplication  of  types,  it  becomes  necessary  to  in- 
dicate their  position.  This  is  done  in  a variety  of  ways.  Thus 
the  letters  of  the  Greek  alphabet  have  been  used. 


/3CH, 

a CHOH 

* COOH 
a — Lactic  acid 


P CH2OH 

a CH2 

* COOH 
P — Lactic  acid 


OH 


Naphthalene 


Abbreviations  for  neighboring  (o  = ortho),  opposite  (p  = 
para),  and  intermediate  (m  = meta)  were  suggested  by  Kekul6 
to  indicate  the  positions  in  connection  with  di-substitution  prod- 
ucts of  benzene. 


[174] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  47 


In  connection  with  the  tri-substitution  products  of  benzene, 
the  abbreviations  for  neighboring  (v)  = vicinal,  (s)  = symmetric 
and  (a)  = asymmetric  were  likewise  suggested  by  Kekule. 


For  more  special  purposes,  special  symbols  have  been  sug- 
gested, as,  e.  g.,  N for  “Nor”  derivatives  of  heterocyclic  com- 
pounds, etc. 

Numbers  have  also  been  used  and  are  being  used  more  and 
more.  Thus  the  ten  isomeric  di-substitution  products  of  naph- 
thalene have  long  been  indicated  by  numbers. 


8 1 


The  Geneva  Congress*  suggested  the  exclusive  use  of  numbers 
and  no  doubt,  thereby  prepared  the  way  for  a simpler  nomen- 
clature. Not  only  are  numbers  used  to  indicate  the  position  of 
type  groups,  but  of  double  bonds,  the  structural  equivalents  of 
hydrogen  as  well. 

The  application  of  these  rules  to  recent  structural  research 
may  best  be  illustrated  with  the  aid  of  a few  formulas. 

1 2 3 4 5 6 7 8 

CH3  CH  : CH  CH2  CH2  C : CH  CH2OH 

I I 

ch3  ch3 

Di-methyl-2, 6-octa-diene-2,6-ol-8;  or  geraniol 


♦See  Tiemann’s  account  of  the  Congress  in  Ber.  d.  d.  chem.  Ges.,  26,  p.  1595.  An 
abridged  account  can  be  found  in  Richter- Anschuetz-Smith,  Organic  Chemistry,  3rd  Am. 
cd.  (1899),  vol.  1,  p.  57. 


[175] 


48 


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1 2 


3 4 5 OH  7 


8 


CHS  C : CH  CH2  CH2  C CH 


ch2 


ch3 


ch3 


Dimethyl-2, 6-octadiene-2,7-ol-6;  or  linalool. 

The  nomenclature  of  organic  chemistry  naturally  reflects  basal 
theories  and  these  again  underlie  classification.  Hence  rational 
nomenclature  and  classification  go  hand  in  hand.  While  the 
Geneva  Congress  paved  the  way,  in  part,  for  a more  rational 
naming  of  carbon  compounds,  it  could  not  get  very  far,  because 
it  had  no  rational  classification  as  a necessary  basis  for  its  delib- 
erations and  rules.  Hence  it  did  not  get  beyond  propositions  for 
the  nomenclature  of  chain  compounds. 


HETEROCYCLIC  COMPOUNDS 


Practically  all  carbocyclic  compounds  are  readily  taken  care 
of  when  referred  to  the  underlying  carbocyclic  hydrocarbons. 
How  these  can  be  classified  has  already  been  pointed  out.  Dif- 
ficulty has  arisen,  however,  in  the  classification  of  heterocyclic 
compounds.  The  conventional  classification,  or  rather  lack  of 
classification,  of  these  compounds  is  one  of  the  serious  drawbacks 
of  our  text  and  reference  works  on  organic  chemistry. 

The  most  important  of  these  are  again  those  oxygen  and  ni- 
trogen compounds  containing  one  or  more  oxygen  or  nitrogen 
atoms  in  the  cycle  or  ring.  But  it  is  a comparatively  easy  mat- 
ter to  classify  them  along  rational  lines,  both  of  chemical  struc- 
ture and  genetic  relationship.  As  before,  the  oxygen  compounds 
will  be  taken  up  first. 

It  has  already  been  pointed  out  that  hydroxy  substitution  in 
connection  with  different  carbon  atoms  of  the  underlying  hydro- 
carbons does  not  produce  new  types.  This  statement  is  true  only 
in  so  far  as  the  hydroxy  substitution  products  themselves  are 
concerned.  This  point  has  been  illustrated  by  a few  well-known 
formulas.  It  has  also  been  pointed  out  that  in  such  compounds 
the  position  of  the  substituting  groups  plays  a more  or  less  im- 
portant role  and  should  be  considered  in  connection  with  the 
classification  of  these  compounds. 


[176] 


KREMERS — THIS  classification  of  carbon  compounds  49 


Thus,  e.  g.,  those  glycols  in  which  the  two  hydroxy  groups  are 
connected  with  different  carbon  atoms  may  be  subclassified  into 
alpha,  beta,  gamma,  etc.,  glycols.  Series  of  such  glycols  may  be 
represented  either  by  their  initial  members  or  by  type  formulas. 


ch2oh 

ch2oh 

ch2oh 

1 

ch2oh 

1 

c.h2 

1 

ch2 

I I 

ch2oh  ch2 

I 

CH2OH,  or 


R'2COH 

R'2COH 

1 

R'2C 

R'2COH 

R'2C 

R'2COH 

1 

R'2COH 

R'2C 

a — Glycols 

/S — Glycols 

1 

R'2COH 

7 — Glycols 

Whereas  those  glycols  which  contain  both  hydroxy  groups  con- 
nected with  the  same  carbon  atom,  as  a rule,  split  off  water  very 
readily,  thereby  yielding  aldehydes  and  ketones,  respectively; 
those  glycols  in  which  the  two  hydroxy  groups  are  connected 
with  different  carbon  atoms  split  off  the  elements  of  water  much 
more  reluctantly.  Moreover,  the  ease  with  which  they  split  off 
water  depends  upon  the  position  of  the  hydroxy  groups.  Thus, 
gamma,  delta  and  epsilon  glycols  yield  a molecule  of  water  from 
the  two  hydroxy  groups  much  more  readily  than  do  the  alpha 
and  beta  glycols,  for  the  reason  that  rings  with  five,  six  and 
seven  members,  are,  as  a rule,  much  more  stable  than  those  with 
three  and  four  members. 

The  classification  of  these  glycols  and  their  corresponding 
oxides  can  best  be  demonstrated  in  two  ways:  first  by  their  deri- 
vation from  the  underlying  hydrocarbons,  and  secondly  by  the 
development  of  homologous  series  from  the  types  thus  established. 


[177] 


50 


BULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


Hydro- 
carbons a-Glycols 


Oxides 


/3-Glycols 


Oxides 


CH, 

ch2oh 

CH2\ 

1 n 

ch3 

j 

ch2oh 

y 

ch2/ 

ch3 

ch2oh 

ch2\ 

CH2OH 

ch2 

1 

1 

1 O 

! 

/ \ 

ch2 

CHOH 

CH/ 

ch2 

CH2  ( 

1 

1 

1 

1 

\ / 

ch3 

ch3 

ch3 

ch2oh 

ch2 

ch3 

ch2oh 

ch3\ 

ch2oh 

ch2 

1 

1 

1 O 

1 

/ \ 

ch2 

CHOH 

CH/ 

ch2 

CH2  ( 

1 

1 

1 

I 

\ / 

ch2 

1 

ch2 

ch2 

CHOH 

CH 

1 

ch3 

1 

ch3 

1 

CH3 

| 

ch3 

1 

ch3 

ch3 

ch2oh 

CH2\ 

ch2oh 

ch2 

1 

1 

1 O 

1 

/ \ 

ch2 

CHOH 

CH/ 

ch2 

CH2  ( 

1 

1 

1 

1 

\ / 

ch2 

1 

ch2 

1 

ch2 

CHOH 

CH 

1 

ch2 

1 

ch2 

ch2 

| 

ch2 

ch2 

1 

CHS 

1 

CH, 

1 

CH3 

1 

ch3 

1 

ch3 

O 


O 


In  the  above  table  only  those  glycols  and  their  corresponding 
oxides  derivable  from  normal  hydrocarbons  have  been  recorded 
simply  as  a matter  of  convenience.  Having  established  the 
types  of  glycols  and  oxides,  it  is  an  easy  matter  to  take  the  first 
member  of  each  series  and  use  it  as  the  starting  point  for  the 
development  of  an  homologous  series. 


[178] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  51 


7-Glycols  Oxides 


5-Glycols  Oxides 


ch2oh 

1 

ch2 

ch2— CH2\ 

1 

1 O 

ch2 

CHi—CHt/ 

I 

ch2oh 


ch2oh 

CH2OH 

1 

ch2 

ch2— ch2 

j 

ch2 

1 

\ 

1 

ch2 

o 

ch2 

1 

/ 

1 

CHOH 

CH2— CH 

ch2 

| 

ch3 

1 

CH3 

j 

ch2oh 

CH2— CH2 

/ \ 

ch2  o 

\ / 

ch2— ch2 


In  a similar  manner  heterocyclic  compounds  with  two  oxygen 
atoms  to  the  cycle  can  be  referred  to  and  derived  from  the  gly- 
cols. Both  the  simple  oxides  (dimethylene  oxide,  trimethylene 
oxide,  etc.)  as  well  as  the  heterocyclic  compounds  with  two  oxy- 
gen atoms  should  be  subordinated,  for  purposes  of  classification, 
to  the  glycols,  as  the  monoxygen  ethers  are  to  the  monatomic 
alcohols. 


[179] 


52 


BULLETIN  OB  THE  UNIVERSITY  OF  WISCONSIN 


Hydro- 


carbons 

a-Diamides 

Cyclic  Imides 

/S-Diamides 

Cyclic  Imides 

ch3 

CH2NH2 

CH2\ 

1 

1 

| NH 

ch3 

ch2nh2 

ch2/ 

ch3 

ch2nh2 

* 

CH2\ 

ch2nh2 

CH2 

1 

1 

| NH 

1 

/ \ 

ch2 

chnh2 

CH/ 

ch2 

CH2  NH 

1 

1 

1 

1 

\ / 

ch3 

CHS 

CH8 

ch2nh2 

ch2 

ch3 

ch2nh2 

CH2\ 

ch2nh2 

ch2 

1 

1 

| NH 

1 

/ \ 

ch2 

chnh2 

CH/ 

ch2 

CH2  NH 

1 

1 

I 

1 

\ / 

ch2 

ch2 

1 

ch2 

chnh2 

1 

CH 

1 

ch3 

1 

ch3 

ch3 

1 

CH, 

1 

ch3 

ch3 

ch2nh2 

CH2\ 

ch2nh2 

ch2 

1 

1 

| NH 

1 

/ \ 

ch2 

chnh2 

CH/ 

ch2 

CH2  NH 

1 

1 

1 

1 

\ / 

ch2 

ch2 

ch2 

chnh2 

CH 

1 

ch2 

1 

ch2 

1 

ch2 

» 1 

ch2 

| 

ch2 

1 

ch3 

ch3 

1 

ch3 

1 

ch3 

1 

ch3 

The  same  principle  of  classification  applies  to  the  heterocyclic 
compounds  with  one  or  more  nitrogen  atoms  in  the  ring.  Those 
with  one  nitrogen  atom  can  be  derived  from  the  corresponding 
diamines  by  deammoniation  as  the  oxides  were  derived  from  the 


[180] 


kremers — the  classification  of  carbon  compounds  53 


7-Diamides  Cyclic  Imides  5-Diamides  Cyclic  Imides 


CH2NH2 

1 

ch2 

ch2— CH2\ 

1 

1 NH 

ch2 

ch2— ch2/ 

CH2NH2 


ch2nh2 

ch2nh2 

1 

ch2 

ch2— CH2\ 

1 

ch2 

ch2— ch2 

1 

NH 

1 

/ \ 

ch2 

CH2— CH  / 

ch2 

CH2  NH 

1 

I 

1 

\ / 

CHNH2 

1 

ch3 

CH3 

ch2 

1 

ch2nh2 

ch2— ch2 

glycols  by  dehydration.  Like  the  alkyl  derivatives  of  the  mon- 
amines, these  cyclic  imines  should  be  subordinated,  for  purposes 
of  classification,  to  the  corresponding  diamines.  The  types  of 
cyclic  imines  referable  to  diamines  of  the  limit  series  are  tabu- 
lated above. 


[181] 


54 


BULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


APPENDIX  A 

ARRANGEMENT  ACCORDING  TO  THE  NUMBER  OF 
CARBON  ATOMS 

The  arrangement  of  carbon  compounds  according  to  the  num- 
ber of  carbon  atoms  or  equivalents  became  possible  only  after 
a large  number  of  organic  compounds  had  been  analyzed.  In 
a way  it  may  be  regarded  as  the  basal  empirical  classification, 
the  importance  of  which  might  easily  be  overestimated  when 
quantitativeness  was  a dominant  thought  in  chemistry.  Strange 
as  it  may  now  seem,  it  does  not  appear  that  such  an  arrangement 
was  seriously  suggested  immediately,  even  after  Liebig  had  per- 
fected the  technique  of  organic  analysis,  thus  making  possible  the 
determination  of  carbon  atoms  or  carbon  equivalents,  much 
less  shortly  after  the  idea  of  quantitativeness  became  the  domi- 
nant idea  in  chemistry  with  the  antiphlogistic  theories  of  Lavois- 
ier. It  is  rather  significant  that  such  an  arrangement  of  organic 
compounds  was  carried  out  in  all  seriousness  in  one  of  the  prin- 
cipal handbooks  of  chemistry  only  after  the  dogmatism  of  the 
first  half  of  the  nineteenth  century  had  caused  the  partial  ship- 
wreck of  organic  theories. 

The  primary  classification  of  carbon  compounds  according  to 
the  number  of  carbon  atoms  was  put  into  practice  in  Lepold 
Gmelin’s  comprehensive  and  extensively  used  Handbuch  der 
Chemie,  the  first  edition  of  which  had  appeared  in  1817,  and 
which  is  best  known  to  English  speaking  chemists  through  Watt’s 
translation  published  by  the  Cavendish  Society. 

A conspicuous  example  of  a modern  text,  or  rather  handbook, 
of  chemistry  in  which  the  same  primary  classification  occurs  is 
the  well  known  Treatise  on  Chemistry  by  Roscoe  and  Schor- 
lemmer,  volume  three  of  which,  the  first  part  of  organic  chem- 
istry, appeared  in  1890. 


[182] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  55 


APPENDIX  B 

CLASSIFICATION  AS  REVEALED  BY  TABLES  OF 
CONTENTS 

One  of  the  earliest  texts  on  chemistry  devoid  of  alchemistic 
jargon  is  that  of  Lemery,  the  first  edition  of  which  appeared 
in  1675.  It  not  only  appeared  in  numerous  editions  during  his 
life  time,  but  its  publication  was  continued  long  after  the  au- 
thor’s death.  Moreover,  it  was  translated  into  English,  Dutch, 
German  and  Italian.  For  more  than  a century  it  exerted  a 
decided  influence  on  chemical  thought.  Like  most  books  of  his- 
torical interest,  Lemery’s  Cours  de  Chymie  is  not  generally  avail- 
able. For  this  reason,  a small  part  of  the  table  of  contents 
(edition  of  1756)  is  herewith  reproduced: 

Lemery,  Cours  de  Chymie 

Des  Mineraux 

I.  De  l’or. 

II.  De  l’argent,  etc. 

Des  Vegetaux 

I.  Du  jalap,  resine  ou  magistere  du  jalap. 

II.  De  la  rhubarbe,  extrait  de  rhubarbe. 

V.  De  la  canelle,  huile  ou  essence  de  canelle,  son  eau  etheree, 
tincture  de  canelle. 

XIX.  Du  sucre,  esprit  de  sucre. 

XXI.  Du  vinaigre,  distillation  du  vinaigre. 

XX.  Du  vin,  distillation  de  vin  et  eau-de-vie,  esprit  de  vin,  etc. 

XXII.  Du  tartre,  crystal  de  tartre,  tartre  soluble  ou  sel  vegetal, 
crystal  du  tartre  chalybe  ou  martial,  tartre  martial 
soluble,  tartre  emetique,  etc. 

XXXII.  Du  camphre. 

Des  Animaux 

I.  De  la  vipre,  destination  de  la  vipre. 

V.  Du  miel,  etc. 

VI.  De  la  cire,  etc. 


[183] 


56 


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The  very  limited  scope  of  the  organic  materia  chemia  at  the 
close  of  the  18th  century  becomes  apparent  from  the  following 
table  of  contents,  viz.  that  of 

F.  A.  C.  Gren:  Grundriss  der  Naturlehre  in  seinem  mathe- 
matischen  und  chemischen  Theile  neu  bearbeitet.  1793. 

Bestandtheile  der  Koerper  der  drey  Naturreiche  (p.  255). 

Mineralische  Substanzen  (p.  256):  Die  Koerper  des  Mineralreiches,  oder 
die  unorganischen  Koerper  lassen  sich  fueglich  in  fuenf  Classen  abtheilen, 
nemlich  Salze,  Erden,  Metalle,  Erdharze,  und  Schwefel. 

Bestandtheile  der  Pflanzenkoerper  (p.  318):  Zu  den  naeheren 
Bestandtheilen  des  Pflanzenreiches  rechne  ich: 

(1)  Schleim  oder  Gummi 

(2)  Harz 

(3)  Kleber 

(4)  Staerkeartigen  Theil 

(5)  Zucker 

(6)  Weinsteinsaeure 

(7)  Sauerkleesalzsaeure 

(9)  Aepfelsaeure 

(10)  Essigsaeure 

(11)  Benzoesaeure 

(12)  Zusammenziehenden  Stoff 

(13)  Fettes  Oel 

(14)  Aetherisches  Oel 

(15)  Kampher 

(16)  Scharfen  Stoff  und 

(17)  Narcotischen  Stoff. 

Bestandtheile  der  thierischen  Koerper  (p.  344) : Als  naehere 
Bestandtheile  des  thierischen  Koerpers  sind  bekannt: 


(1)  Gallerte 

(2)  Fett 

(3)  Lymphe 

(4)  Fadenartiger  Theil 

(5)  Knochenmaterie  und 

(6)  Milchzucker 

(7)  Ameisensaeure  und 

(8)  Das  scharfe  Harz  der  spanischen  Fliegen. 

[184] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  57 


Practically  the  same  list  of  “naeheren  Bestandtheilen,  die  als 
solche  in  Koerpern  des  Gewaechsreiches  praeexistime”  is  enum- 
erated in  Gren’s  Systematisches  Handbuch  der  gesamten  Chemie 
of  1794  (vol.  2,  p.  3). 

That  the  number  of  organic  substances  had  grown  but  little 
shortly  after  Lavoisier’s  death  becomes  apparent  from  the  fol- 
lowing list.  Though  Lavoisier’s  point  of  view  is  primarily  that 
of  oxygen  and  combustion  the  distinction  between  vegetable 
and  animal  acids  is  clearly  marked. 

A.  Lavoisier:  Traite  elementaire  de  chimie , 1801. 

Lavoisier’s  point  of  view  is  that  of  oxygen:  oxidation  and 
combustion.  Having  considered  the  four  simple  combustible 
substances,  viz.,  phosphorus,  sulphur,  carbon,  and  hydrogen, 
he  turns  to  the  combustion  of  vegetable  fats.  This  leads  him  to 
the  consideration  of  “the  composition  of  vegetable  and  animal 
substances’’  in  general  (I,  p.  123).  Those  substances  related  to 
carbonic  acid,  the  product  of  combustion,  are  naturally  of  prime 
interest  to  him.  He  names  them,  in  accordance  with  his  system 

of  nomenclature  of  mineral  acids,  as  follows: 

♦ 

Vegetable 
L'acide  aceteux 
L’acide  acetique 
L’acide  oxalique 
L’acide  tartareux 
L’acide  pyro-tartareux 
L’acide  citrique 
L’acide  malique 
L’acide  pyro-muquex 
L’acide  pyro-ligneux 
L’acide  gallique 
L’acide  benzolque 
L’acide  camphorique 
L’acide  succinique 

The  same  point  of  view  naturally  leads  him  to  take  up  next 
the  products  of  destructive  distillation  (I,  p.  132)  of  vegetable 
and  animal  substances,  among  which  he  mentions  Dippel’s  oil. 

Inasmuch  as  carbonic  acid  is  one  of  the  principal  products  of 
the  fermentation  of  saccharine  liquids,  the  process  of  vinous 

[185] 


Animal 

L’acide  lactique 
L’acide  saccho-lactique 
L’acide  bombique 
L’acide  formique 
L’acide  sebacique 
L’acide  prussique 


58 


BULLETIN  OF  The  UNIVERSITY  OF  WISCONSIN 


fermentation  comes  next  (p.  139)  to  be  followed  by  putrid  fer- 
mentation (p.  153)  and  acetous  fermentation  (p.  159). 

The  consideration  of  acids  is  followed  by  that  of  the  salts,  the 
organic  (pp.  277-322)  following  the  inorganic  (pp.  231-276). 

A more  compendious  list  is  enumerated  in  the  ten  volume 
works  of 

A.  F.  Fourcroy:  Systeme  des  connaissances  chimiques , 1800. 
On  vegetable  organic  compounds  (Volume  7). 


1.  Juice 

2.  Mucous,  mucilage  and  gums 

3.  Sugar 

4.  Vegetable  acids 

A.  “Acids  natifs  et  purs.” 

(a)  Gallic  acid 

(b)  Benzoic  acid 

(c)  Succinic  acid 

(d)  Malic  acid 

(e)  Citric  acid 

B.  “Acidules” 

(a)  Oxalic  acid 

(b)  Tartarous  acid 

C.  “Acides  empyreumatiques.” 

(a)  Pyromucous  acid 

(b)  Pyrotartarous  acid 

(c)  Pyroligneous  acid 

D.  Acids  not  found  as  such  in  nature 

(a)  Mucous  acid 

(b)  Camphoric  acid 

(c)  Suberic  acid 

E-  Artificial  acids  corresponding  to  natural  acids 

(a)  Malic  acid 

(b)  Tartarous  acid 

(c)  Oxalic  acid 

F.  Acids  produced  by  fermentation 

(a)  Acetous  acid 

(b)  Acetic  acid 

5.  Farinaceous  substance 

6.  Gluten 

7.  Extractive 

8.  Fixed  oil 


[186] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  59 


9.  Fat  and  wax 

10.  Volatile  oil 

11.  Camphor 

12.  Resins 

13.  Gum-resins 

14.  Caoutchouc 

15.  Balsams 

16.  Pigments 

17.  Vegetable  albumen 

18.  Woody  substance 

19.  Tannin 

20.  Cork 

21.  Fossil  and  mineral  substances 


This  classification  according  to  the  three  natural  kingdoms 
with  the  sub-classification  of  phytochemistry  and  zoochemistry 
not  only  extended  to  the  systems  of  Berzelius  and  Liebig,  but 
still  finds  its  way  into  the  lumber  chambers  of  unclassified  com- 
pounds of  modern  organic  chemistries.*  That  it  should  have 
constituted  the  fundamental  classification  of  phytochemistry  as 
late  as  the  seventies  of  the  last  century  is,  therefore,  not  surpris- 
ing. The  same  conservatism  went  one  step  farther  when  phar- 
maceutical authors  dignified  this  abandoned  chemical  point  of 
view  by  calling  it  a “pharmaceutical”  classification  of  chemicals. 

To  what  extent  organic  chemistry  was  the  chemistry  of  plant 
constituents  even  in  1837  becomes  apparent  from  the  following 
partial  table  of  contents  taken  from  Woehler’s  translation  of 
Berzelius’  Lehrbuch  der  Chemie. 

NAEHERE  BESTANDTHEILE  PFLANZEN 

I.  Klasse:  Pflanzensaeuren  (with  thirty- three  titles). 

II.  Klasse:  Vegetablische  Salzbasen  (with  twenty-two  titles). 

III.  Klasse:  Indifferente  Pflanzentoffe. 

1.  Staerke 

2.  Gummi  und  Pflanzenschleim 

a.  Gummi 

b.  Pflanzenschleim 


* E.  g.,  Richter- Anschuetz-Smith,  vol.  2,  pp.  334,  et.  seq. 


[187] 


60 


BULLETIN  OE  The  UNIVERSITY  OE  WISCONSIN 


3.  Zucker 

a.  Rohr  zucker 

b.  Traubenzucker 

c.  Mannazucker 

d.  Schwammzucker 

e.  Suessholzzucker 

4.  Pflanzenleim  und  Pflanzeneiweiss 

5.  Pectin  und  Pectinsaeure 

6.  Pollenin 

7.  Fette  Oele 

(c)  Trockende  Oele 

(2)  Nicht  “ “ 

(3)  Feste  Oele 

Seifenbildungsprocess  und  seine  Producte 

a.  Eigentliche  fette  Saeuren,  d.  h.  solche,  welche  bei  der  Destina- 

tion mit  Wasser  nicht  mit  uebergehen 

b.  Durch  den  Seifenbildungsprocess  erzeugte  fluechtige  Saeuren 

c.  Glycerin  oder  Oelzucker 

d.  Seife 

Einfluss  der  Saeuren  bei  der  Zersetzung  der  Oele 
Fluechtige  Oele 

a.  SauerstofFfreie  fluechtige  Oele 

b.  Sauerstoffhaltige  “ “ 

(a)  Aromatische  Oele 

(b)  Scharfe  und  blasenziehende  Oele 

(c)  Blausaeurehaltige  giftige  Oele 

(d)  Campher 

Harze 

Extracte  und  extractfoermige  Stoffe 

A.  Rothe  Pflanzenfarben 

B.  Gelbe 

C.  Gruene  “ 

D.  Blaue  “ 

Skelett  der  Pflanzen 

a.  Mark 

b.  Holz  und  Pflanzenfaser 

c.  Rinde 

Von  den  fett-und  harzhaltigen  Milchsaeften  der  Pflanzen  und  den  sogenannten 
Gummiharzen 
Wurzeln 
Rinden 
Holzarten 

Kraeuter  und  Schwaemme 

Blaetter 

Bluethen 

Fruechte  und  Samen 


[188] 


KREMERS — THE  CLASSIFICATION  OF  CARBON  COMPOUNDS  61 


APPENDIX  C 

DEFINITIONS  OF  ORGANIC  CHEMISTRY 

Gmelin.  “The  bodies  of  the  organic  kingdom  are  distin- 
guished, in  their  most  complete  state,  from  those  of  the  inor- 
ganic kingdom: 

1.  By  their  inherent  vital  force. 

2.  By  a peculiar  structure,  internal  and  external. 

3.  By  being  composed,  for  the  principal  and  most  important 

part  at  least,  of  chemical  compounds  quite  peculiar  to 
them,  called  Organic  compounds,  or  Proximate  prin- 
ciples of  the  organic  kingdom,  which  occur  in  the 
bodies  of  plants  and  animals,  partly  mixed  and  partly 
combined,  both  with  one  another  and  with  certain  in- 
organic compounds.” 

“The  proximate  principles  into  which  an  organic  body  may 
be  resolved,  either  by  mechanical  or  by  chemical  means,  are 
partly  inorganic,  .such  as  water,  carbonic  acid,  and  other  mineral 
acids;  partly  organic.  When  the  latter  are  of  such  a nature, 
that  any  attempt  to  decompose  them  further  leads  to  the  forma- 
tion of  decomposition  products,  which  when  reunited,  produce 
something  totally  different  from  the  substance  originally  decom- 
posed, they  are  regarded  as  Primary,  or  Elementary  Organic 
Compounds.” 

Handbook  of  Chemistry.  Translation  of  the  4th  edition.  Vol. 
7,  p.  1. 

Gerhardt.  “Die  organische  Chemie  hat  die  Aufgabe,  die 
Koerper,  welche  durch  die  Verbindung  dieser  Elemente  (namely 
carbon,  hydrogen,  nitrogen  and  oxygen,  and  occasionally  sulphur, 
phosphorus,  metals,  etc.)  entstehen,  zu  untersuchen,  und  zwar 
in  Beziehung  auf  ihre  Eigenschaften,  ihre  Zusammensetzung 
und  auf  die  Gesetze,  nach  welchen  ihre  Verwandlungen  erfolgen. 
Da  alle  organischen  Verbindungen  ohne  Ausnahme  Kohlenstoff 
enthalten,  so  koennte  man  die  organische  Chemie  die  Chemie 

[189] 


62 


BULLETIN  OF  THE  UNIVERSITY  OF  WISCONSIN 


des  Kohlenstoffs  nennen.  Sie  betrachtet  die  organischen  Sub- 
stanzen  nur  in  ihren  rein  chemischen  Beziehungen,  ohne  Rueck- 
sicht  auf  ihre  Rolle  im  Organismus  . . . ” 

“Alle  Gebilde,  Secretionen  und  Organe  des  Pflanzen-und 
Thierkoerpers  sind  Mischungen  von  organischen  Stoffen  in  ver- 
schiedenen  Verhaeltnissen.  Die  organische  Chemie  gibt  die  Mit- 
tel  an,  diese  bestimmten  Bestandtheile,  deren  Zusammensetzung 
unter  denselben  Umstaenden  genau  dieselbe  und  unveraender- 
lich  ist,  von  einander  zu  trennen  und  sie  in  dem  Zustande  der 
Reinheit  darzustellen.  Sie  allein  gehoeren  ins  Gebiet  der  or- 
ganischen Chemie.’' 

Grandriss  de  organischen  Chemie.  Aus  dem  Franzoesischen 
uebersetzt  von  A.  Wurtz,  Strassburg,  1844,  vol.  1,  pp.  142. 

Kekule.  “Wir  sind  also  zu  der  Ueberzeugung  gelangt,  dass 
die  chemischen  Verbindungen  des  Pflanzen-und  Thierreichs  die- 
selben  Elemente  enthalten  wie  die  Koerper  der  leblosen  Natur; 
wir  haben  die  Ueberzeugung,  dass  in  ihnen  die  Elemente  den- 
selben Gesetzen  folgen;  dass  also  weder  in  dem  Stoff,  noch  in 
den  Kraeften  und  ebensowenig  in  der  Anzahl  oder  in  der  Art 
der  Gruppirung  der  Atome  ein  Unterschied  besteht  zwischen 
den  organischen  und  den  unorganischen  Verbindungen.  Wir 
sehen  eine  fortlaufende  Reihe  chemischer  Verbindungen,  deren 
einzelne  Glieder  (wenn  man  nur  die  nahe  liegenden  vergleicht) 
eine  so  grosse  Aehnlichkeit  zeigen,  dass  naturgemaess  nirgends 
eine  Trennung  gemacht  werden  kann.  Wenn  aber  dennoch 
eine  Trennung  vorgenommen  werden  soil,  wie  sie  in  der  That, 
einzig  im  Interesse  der  Uebersichtlichkeit,  vorgenommen  werden 
muss,  dann  ist  diese  Trennung  an  sich  nicht  natuerlich,  sie  ist 
rein  willkuerlich  und  man  kann  eben  darum  die  Grenze  da  ziehen, 
wo  es  gerade  zweckmaessig  scheint.  Will  man  dabei  so  theilen, 
dass  moeglichst  das,  was  gewohnheitsmaessig  in  der  organ- 
ischen Chemie  abgehandelt  wurde,  auch  jetzt  als  besonderer 
Abschnitt  abgehandelt  werde,  so  erscheint  es  am  zwechmaessig- 
sten,  wie  dies  in  neurer  Zeit  schon  oefter  vorgeschlagen  wurde, 
alle  Kohlenstoffverbindungen  in  diesem  Abschnitte  zusammen 
zu  fassen. 

“Wir  definiren  also  die  organische  Chemie  als  die  Chemie  der 

[190] 


kremers-the  classification  of  carbon  compounds  63 


Kohlenstoff  verbindungen . Wir  sehen  dabei  keinen  Gegensatz 
zwischen  unorganischen  und  organischen  Verbindungen.  Das 
was  wir  mit  dem  althergebrachten  Namen  organische  Chemie 
bezeichnen  und  was  man  zwechmaessiger  Chemie  der  Kohlen- 
stoffverbindungen  nennen  wuerde,  ist  vielmehr  nur  ein  specieller 
Theil  der  reinen  Chemie,  den  wir  desshalb  besonders  abhandeln, 
weil  die  grosse  Anzahl  und  die  besondere  Wichtigkeit  der  Kohl- 
enstoffverbindungen  ein  specielleres  Kennenlernen  derselben 
noethig  erscheinen  laesst.” 

Lehrbuch  der  organischen  Chemie , vol.  1,  p.  10.  A transla- 
tion of  this  page  may  be  found  in  Roscoe  and  Schorlemmer, 
Treatise  on  Chemistry,  vol.  3,  Part  1,  32. 


|191] 


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